PHY. 
fiTHYQI 



' s$«$^n^c^Snc^J^S^SS^sSn! 





~>*&m m 



Class _ 

Book. 




Copyright N?._ 



COPYRIGHT DEPOSIT. 



: 






m,.,g/A 



X-RAY PICTURE OF HAND 



PHYSIOLOGY AND HYGIENE 
FOE YOUNG PEOPLE 



BY 
ROBERT EADIE 

PRINCIPAL OF SCHOOL 72, BOROUGH OF QUEENS 
NEW YORK CITY 

AND 

ANDREW EADIE, M.D. 

PROFESSOR OF PHYSIOLOGY, ONTARIO MEDICAL COLLEGE 
FOR WOMEN, TORONTO, CANADA 



NEW YORK 
CHARLES SCRIBXER'S SONS 

1909 







Copyright, 1909, by 
CHARLES SCRIBNER'S SONS 




CU.A, 244 217 
JUL 28 f909 

i. i ■ 



PREFACE 

It is realized to-day, as perhaps never before, that our most 
precious possession is good health. There never was a time 
when greater effort was put forth to make it possible for chil- 
dren to grow up with strong, healthy bodies, and for grown 
people to live and do their work under healthful conditions. 
In the preparation of this book the authors have made it their 
chief aim to present the essential facts of personal, domestic, 
and public hygiene in such a way as to render the book an 
efficient ally of the forces that are working for healthy living. 

A man entrusted with the care and running of a machine far 
less intricate than the human body is expected to know all its 
parts, and their relations to one another, before he is fitted to run 
the machine at its greatest efficiency. It is equally reasonable to 
expect that one is best fitted to care for his body, the machine 
with which he must do all his work, only when he knows its 
parts and the work that each should perform. Accordingly, in 
this book a sufficient amount of anatomy and physiology of the 
organs of the body is given to make their hygiene intelligible. 

In order that the relation of the parts of the body may be best 
understood, these parts are considered under the three great 
functions bv which life is maintained, viz., nutrition, movement, 



iv PREFACE 

irritability and control. The organs concerned in each function 
are thus studied in their relation to each other; and the function, 
instead of an isolated organ, forms the unit of study. 

Before treating of a function as performed in the human body, 
this book shows how the same function is performed by plants 
and lower animals. This treatment furnishes the proper se- 
quence to the nature study of the lower grades. It gives to 
pupils of the elementary schools a new and larger interest in 
living things; and, for those who go on to a high school, it 
affords a desirable introduction to the study of biology. 

This book complies with the laws of those States which re- 
quire that twenty-five per cent, of the text shall treat of "the 
nature and effects of alcoholic drinks and other narcotics." It 
is believed that the method of treatment herein employed will 
commend itself to the best judgment of those who are solicitous 
for the future welfare of the school children of to-day. 



CONTENTS 
PART I- LIVING THINGS AND FOOD 

CHAPTER • PAGE 

I. Living Things 1 

II. Kinds of Food and Their Uses 14 

III. Cooking 31 

IV. Drinks Which Contain Alcohol 43 

PART II— THE FUNCTION OF NUTRITION 

V. Plant Nutrition 49 

VI. Animal Nutrition ... ....... 55 

VII. Digestion 67 

VIII. The Circulation of the Blood ...... 91 

IX. Is Alcohol a Food? 115 

X. Breathing 123 

XI. The Skin and the Kidneys . 141 

PART III— THE FUNCTION OF MOVEMENT 

XII. Plant and Animal Movements 168 

XIII. The Bones 177 

XIV. The Muscles 195 

XV. Physical Exercise 207 

v 



vi CONTENTS 

PART IV— THE FUNCTION OF IRRITABILITY AND 

CONTROL 

CHAPTER PAGE 

XVI. Plant and Animal Irritability and Control . 215 

XVII. The Organs of the Nervous System . . . 229 

XVIII. The Effects of Narcotics on the Nervous 

System .............. 253 

XIX. The Five Special Senses ........ 264 

PART V— DOMESTIC AND PUBLIC HYGIENE 

XX 283 

Appendix 306 

Keys ................ 341 

Glossary 343 

Index 349 



PHYSIOLOGY AND 
HY^GIENE FOR YOUNG PEOPLE 



PHYSIOLOGY AND 
HYGIENE FOR YOUNG PEOPLE 

PART I— LIVING THINGS AND FOOD 
CHAPTER I 

LIVING THINGS 

It is often supposed that all living things can be divided into 
two distinct classes, plants and animals. Common animals are 
so different from common plants that it has always been easy to 
distinguish between them. A horse seems to us so different from 
a tree in whose shade it may be standing that we never think of 
putting them in the same class. Without any hesitation we say 
the horse is an animal and the tree is a plant. 

But since living things came to be studied with the aid of a 
microscope, very small living things have been discovered which 
before were not known to exist. Some of these minute things re- 
semble both plants and animals, and it is difficult to tell to which 
class they belong. In fact, it is impossible to fix upon any dis- 
tinction between plants and animals by which all plants can be 
separated from all animals. 

Although living things differ much in form, size, and appear- 
ance, yet they all do the same things, i. e.> perform the same 

junctions , in order to keep alive. Plants and animals, both large 

1 



2 PHYSIOLOGY FOR YOUNG PEOPLE 

and small, keep themselves alive by performing the same func- 
tions, though not in the same way. 

One of these functions is the taking of food into their bodies 
and using it up. A tree does not take in food in the same way 
that we do. Yet all living things, plants and animals alike, must 
take in and use up food in order to keep alive. In using up 
food, both plants and animals need to get oxygen from the air. 
They do not all get oxygen in the same way. We get it through 
our lungs, fish get it through their gills, common plants get it 
through their leaves; but plants and animals make the same use 
of oxygen in their bodies, no matter how they get it from the air. 

Another function which plants and animals have in common 
is the power of movement. The animals that we know move 
about very freely. They need this power in order to secure 
food, to obtain shelter, and to protect themselves from enemies. 
Yet plants, as we shall see, make many movements, though 
their movements are slower and less noticeable than those of 
common animals. 

Still another function that is common to both plants and ani- 
mals is the power to adjust themselves more or less completely 
to the world around them. They have the power to seek those 
conditions of light, heat, moisture, etc., that are comfortable and 
helpful, and to avoid, to some extent, those conditions that are 
harmful or uncomfortable. The higher animals have nerves 
that greatly aid in doing this; but plants and lower animals 
that have no nerves perform the same function. 

In your earlier study of physiology you learned something 



LIVING THINGS 




about the organs of the human body and the functions they 
perform in keeping the body alive. You probably formed the 
opinion that physiology treats only of the functions performed 
by the human body. But physiology treats of the 
functions performed by all living things, of which 
the human family is only a small part. 

With this book you will continue your studies con- 
cerning the human body and how to take care of it. 
You will learn more fully about its different parts 
and how they w r ork together to maintain life and to 
promote the health of the body. You will learn 
something also of the w T ay in which other living 
things keep themselves alive. Y r ou will have a new 
interest in the plants and animals that you see about 
you when you realize that they 
maintain their lives by performing 
the same functions as are per- 
formed in the human body. 

Cells. — Living things, whether l- Nucleus 

& fe ' 2. Fibre 

plants or animals, are made up of 3 a ^ r end h of 
small, living particles called cells. 
The word cell is often used to mean a space 
surrounded by walls, as when we speak of a 
cell of a prison or a cell of a honey-comb. The 

cells of most plants have walls, which enclose the living matter. 

Some animal cells have walls, but others have none; they are 

just little naked specks of living material. 




ONE KIXD 

OF XERVE 

CELL 



OXE KIND OF 
CELL SHOW- 
ING NUCLEUS 
W I T H I X THE 
PROTOPLASM 



4 PHYSIOLOGY FOR YOUNG PEOPLE 

Cells vary greatly in size. Most cells cannot be seen without 

a microscope. They usually vary from .^far to nrVc" of an 

inch in diameter. The natural form of a cell is spherical, like 

a ball; but when cells are crowded together 

/S^^^C ^ e y assume different shapes. 

/ I^S^^T l ^ n a g encra l wa y^ a ce H somewhat resembles 

\ lOy^*/ * n a PP earan ce a tiny bit of transparent jelly, in 

^y which there is a smaller, denser part. The 

jelly-like, living substance of a cell is colorless 

1. Nucleus 

and is called protoplasm. The work of the cell 
is done by the protoplasm, and, in fact, all the work done in the 
body is done by the protoplasm of its different cells. The 
smaller, denser part in the interior of a cell is called the nucleus. 
A nucleus appears to be necessary to the life of every cell. 

The substance of a living cell is always changing. It is con- 
stantly wearing out, and new matter is being made to take the 
place of what is worn out. A worn-out particle of a cell is cast 
off as waste matter, but the cell repairs itself by taking in food 
and using it to renew its own body. A living cell, then, is not 
composed of exactly the same material from day to day. Parti- 
cles of the cell die and are replaced by new particles, but the cell 
as a whole continues to live. 

Amoeba. — In the lowest kinds of plants and animals the whole 
body consists of one cell. The amoeba, which lives in stagnant 
water, is a common example of a one-celled animal. Although 
it is so small that it can be seen only with a microscope, it is a 
complete animal, for it can move itself about and assume different 



LIVING THINGS 



shapes; it can take food into its body and digest it; it can take 
in oxygen and give out waste matter; and, finally, when full- 
grown, it can divide through the centre and form two amoebas 
like the original. 

The higher kinds of animals and plants consist of millions of 
cells. Each of these cells, acting separately, takes in food, and 
grows. When it is mature, it may divide and produce other 
cells. Cells that are similar and fitted for the same kind of 
work are arranged in groups, or masses, called tissues. As the 
wall of a house is made up of bricks held together by cement, so 
the various tissues are built up of cells held together by cement- 
ing material. The bricks in a wall cannot make the cement that 
holds them together, but the living cells of the tissues make their 
own cementing material. 

Animal tissues. — In the body of a higher animal there are 
different kinds of tissues, which are 
joined so as to make up the entire body. 

Epithelial tissue.— The simplest kind 
of tissue is epithelial tissue, or epitheli- 
um, composed of cells held together by 
a very small amount of cementing ma- 
terial. As a rule, epithelium is spread 
out into a thin membrane. It is used to 
cover a surface, and to line the cavity of 
a hollow organ. The skin of the human body has a thin cover- 
ing of epithelium, and epithelium forms a thin lining for the 
lips, throat, stomach, intestine, and other parts. 




ONE KIND OF EPITHE- 
LIUM 




6 PHYSIOLOGY FOR YOUNG PEOPLE 

Connective tissue. — This kind of tissue connects and binds 
together the cells, tissues, and parts, so as to make one whole 
body. One peculiarity of connective tissues is that they are 

made up of a small num- 
ber of cells and a very 
large amount of cement- 
ing, or intercellular ma- 
terial, that is, material 
between the cells. 
There are several kinds 

ONE KIND OF CONNECTIVE TISSUE p ,« ,• 

of connective tissue, 
which differ greatly in appearance. Among these are included 
cartilage, bone, blood, and fat. 

In some varieties of connective tissue the intercellular material 
is in the form of thin sheets and fibres. In bone, the intercellular 
material is largely composed "of lime, which makes the bones 
firm and hard. In blood, the intercellular material is a fluid. 
Fatty tissue is found in larger or smaller quantity in almost all 
parts of the body. It consists of connective tissue in which 
the cells are distended and filled with fat, which is fluid at the 
ordinary temperature of the body. 

Muscle tissue. — In animals whose bodies are composed of 
different kinds of tissue each tissue has its special work. The 
tissue that has the special work of producing movement is muscle. 
Muscle in a body does not consist of one mass, but of different 
bundles of tissue, each bundle being called a muscle. When 
muscle tissue is examined under a microscope, it is seen to be 



LIVING THINGS 7 

made up of small cells that are elongated into threadlike struc- 
tures called fibres. These fibres are held together by connective 
tissue. 

. Nerve tissue. — Still another kind of tissue is nerve tissue. 
It is composed of cells that are supported and held together 
by a special kind of connective tissue. Extending from 
the cells are fine threads, or prolongations of the cells. Some 
of these prolongations form nerve fibres, which are bound 
together by connective tissue into strands and form the 
nerves. 

Organs. — Tissues are grouped together to form organs. Each 
organ has a special work to do which is called its function. The 
heart is an organ. It is composed of different kinds of tissue 
grouped together, and its function is to force blood through the 
body. The stomach is an organ whose function is to digest food. 
Although each organ has a special work to do, yet it does that 
work for the benefit of all parts of the body. 

Many organs are very delicate, and so we find them placed in 
hollow cases of bone, called cavities, to keep them from being 
iniured. The brain, which is the organ of the mind, is shut up 
in the skull, and many important organs are placed in the large 
cavities of the trunk. 

Look at the picture on page 8, and you will see the ribs 
and the breastbone, which protect the organs in the chest cav- 
ity. Behind the ribs are the organs called lungs. In the centre 
of the neck you can see the tube called the windpipe, which ex- 
tends upward from the lungs. The air that you breathe passes 




im 



A VIEW OF THE INSIDE OF THE TRUNK 

(See Appendix for Key) 

8 







/ 








v Li 


: 


i 


A 




ljf 


'" 




I 




lr^ 










1 










■■Ml ■ 






Bj^^ 4 - 




w\ 






\ 






! 












• 












1 










1 ' ■ 
1 

■ 

•1 


^ 








1 



ANOTHER VIEW OF THE INSIDE OF THE TRUNK 



(See Appendix for Key) 
9 



10 PHYSIOLOGY FOR YOUNG PEOPLE 

through the windpipe into the lungs. Both the lungs and the 
windpipe have been colored purple in the picture. 

Look at the picture on page 9. The ribs have been taken 
off, one lung has been taken out, and the other lung has 
been drawn back so that you may see the cavity of the chest. 
There you see the heart, which is colored red. Above the heart 
are blood tubes, colored red and blue, that go from it to other 
parts of the body. Just under the heart and lungs you can see 
the partition, called the diaphragm, that separates the chest from 
the abdomen. Below the diaphragm is the organ called the liver. 
Below the liver is the stomach. In the picture the liver has been 
colored brown, and the stomach yellow, with red lines over it. 
A tube called the esophagus goes from the mouth down to the 
stomach. It is just behind the windpipe, and so cannot be shown 
in the picture. It is through this tube that food passes from the 
mouth to the stomach. Below the stomach, neatly folded and 
curled up, is the intestine, in which the process of digestion is 
completed. 

The human body. — The human body is not a mere collection 
of cells grouped together in a complex system. It is a carefully 
designed and beautifully furnished home in which the mind 
dwells. The health and vigor of the mind depend very much 
upon the health and vigor of the body. If we would have a 
strong, pure, and noble mind, we should give it a clean, healthy, 
and vigorous body to dwell in. But we cannot do this unless we 
know something about the body and the laws of health that 
govern it. If we are ignorant about these matters we are likely 



LIVING THINGS 11 

to do many things that injure and weaken the body and keep 
the mind from developing as it should. There are three impor- 
tant branches under which we can study the body. These 
branches are anatomy, "physiology, and hygiene. 

From the study of anatomy we learn the shape, size, and 
bcation of the various organs and tissues of the body. 

From the study of physiology we learn the uses, i. e. y the 
functions, of the different organs and parts of the body. 

From the study of hygiene we learn how to take care of the 
body and keep it in health. 

Since good health is the most precious possession we can have, 
it becomes the duty of every one to observe the rules of living 
that tend to promote good health, and to refrain from what- 
ever tends to injure it. A world-wide experience shows that 
one of the greatest causes of impaired health and bodily suffer- 
ing is the use of alcoholic liquors, tobacco, and other narcotics. 
Because of this well-known tendency of alcoholic liquors to 
impair health and to unfit the body for doing its best work, 
many business men require their employees to refrain from the 
use of such liquors. This is especially true of employees in 
responsible positions. Many athletes and professional men, 
too, refrain from the use of alcoholic liquors in order that they 
may keep their bodies in the best condition for performing ex- 
acting duties that call for the greatest endurance or the high- 
est skill. Statements to this effect, such as the following, are 
easily obtainable in large numbers. 



12 PHYSIOLOGY FOR YOUNG PEOPLE 

Worcester Electric Contract Company 

Worcester, Mass., January 25, 1909. 
Dear Sir: — I am opposed to the use of alcoholic liquors in any 
amount by my employees, at any time, and will not take into my 
employ such persons as I know occasionally or frequently use them. 
Very truly, 

Roger T. Morris, 

President and Manager. 

New York, January 23, 1909. 
Dear Sir: — In reply to yours of January 4th, I will say that I 
have never used alcoholic liquors, and would strongly advise against 
the use of the same in athletic work. 

Very truly yours, 

Christy Mathewson, 
New York Base-ball Team, National League. 

Sir Frederick Treves, a distinguished surgeon of London, 
England, said in a recent address : "The man who works on 
even a moderate amount of alcohol is not at his best. The use 
of alcohol is absolutely inconsistent with a surgeon's work, or 
with any work demanding quick, alert judgment." 

SUMMARY 

1. Plants and animals keep themselves alive by performing the same 
functions. 

2. One of these functions is to take in food and oxygen and use them up. 

3. Another function is movement. 

4. The third of these functions is the seeking of conditions that are help- 
ful, and the avoiding, as far as possible, of conditions that are hurtful. 

5. Plants and animals are made up of one or more cells. 

6. Two important parts of a cell are the protoplasm and the nucleus. 



LIVING THINGS 13 

7. The substance of a living cell is constantly wearing out, but the cell 
replaces its worn-out matter. 

8. Similar cells are massed together to form tissues. 

9. Tissues are grouped together to form organs. 

10. Epithelial tissue is used to cover a surface, and to line the cavity of 
a hollow organ. 

11. Connective tissue binds together cells, tissues, and organs to form 
one body. 

12. The work that an organ or part of the body does, is called its func- 
tion. 

13. The body is a home for the mind to dwell in. 

14. The study of the body includes its anatomy, its physiology, and its 
hygiene. 



CHAPTER II 
KINDS OF FOOD AND THEIR USES 

Eating. — If you should travel about the earth and visit different 
zones, you would find that the people living in different cli- 
mates eat different kinds of food. In the frozen north, the 
Eskimo's favorite food is blubber and other fat. In the sunny 
tropics, nobody can eat blubber; but everybody likes fruit. In 
countries that are neither very hot nor very cold, the inhabitants 
prefer a mixed diet of meat, bread and butter, fruit and vege- 
tables. But though diet varies in different climates, the food 
that is eaten in each supplies the material that is needed to 
support life. 

Making new tissue and repairing old.— Your body is not 

made up of the same particles from day to day. The material 

composing the cells of its tissues is constantly wearing out. 

Tiny worn-out particles of these cells are cast off as waste 

matter and are replaced by new material. In this way almost 

every part of your body is changed by slow degrees. The 

change, however, is so gradual and the repair is so complete 

that no difference can be seen in your appearance except after 

a considerable time. The new particles are made out of material 

supplied by the food that you eat. Without food the building-up 

and repairing stop, while the wearing-out goes on more and 

14 



KINDS OF FOOD AND THEIR USES 15 

more rapidly. When a man is starving, he becomes lighter 
every day because his tissues are wasting away and he is taking 
no food to make new tissue. 

Growth of the body. — In childhood and in youth food is 
needed not only for the repair of the tissues, but for their 
growth. You are larger now than you were two years ago, and 
two years hence you will probably be larger than you are now. 

The rate of growth varies at different ages and in different 
children. It declines steadily after about the sixteenth year, 
and usually ceases about the twenty-fifth year. 

Plain wholesome food, pure drinking water, exercise in the 
open air, regular and sufficient sleep are necessary for the 
healthy growth of the body. 

Children sometimes have what are called growing pains 
in the arms and legs. These pains are not due to growth. 
Growth is painless. Pains in the arms and legs of young per- 
sons are a sign of disease, and should be regarded as nature's 
warning that something is wrong. The advice of a physician 
should be obtained without delay in all such cases. 

Bodily heat.— The proper bodily temperature is 98.6° F. 
If it gets much lower than that, the body suffers just as surely 
as a plant suffers in the frost. Yet heat is constantly leaving 
the body, and we should grow too cold unless a fresh supply 
was furnished. This supply must come from food. 

The power to work. — Besides being used for repair, growth, 
and bodily heat, food is needed to produce the power to work, 
or even to move. 



16 PHYSIOLOGY FOR YOUNG PEOPLE 

Food substances.— No one kind of food can supply all the 
different materials that are needed to build up the body, and 
to furnish it with heat and the power to work. Some food sub- 
stances furnish chiefly building material, some furnish chiefly 
heat and the power to work. There are four kinds of food 
substances: (1) Proteids, (2) Carbohydrates, (3) Fats, (4) Salts 
and Water. All of them, in varying amounts, are necessary to 
keep the human body in its best condition; and the best diet is 
a " balanced diet" from which a person can get the four food 
substances in the quantities that he needs. All of the many 
articles of diet on our tables are made up of one or more of 
these four substances. 

Proteids. — The proteids are sometimes called animal foods, 
because lean meat consists largely of proteid, but cereals and 
some other vegetables also contain proteid. Carbon, oxygen, 
hydrogen, and nitrogen are all found in proteids. Proteids 
have been called nitrogenous food because they supply us with 
nitrogen. Another name for proteids is tissue foods; still an- 
other is flesh formers. Without proteid food there can be no 
building up or repairing of the tissues. 

Albumen. — There are four principal kinds of proteids. You 
probably eat some of each kind every day. For example, the 
white of egg is a form of proteid. It is called albumen, and is 
an important article of diet. It is proteid in a concentrated 
form. The yolk, too, contains proteid matter, and is rich in fat. 
Eggs contain also a small amount of mineral matter and a 
trace of sugar. 



KINDS OF FOOD AND THEIR USES ' 17 

Myosin. — If you were asked if you had ever eaten myosin, 
you would probably answer no; yet you eat it every time that 
you eat lean meat. Lean meat consists chiefly of muscle, and 
myosin is the most important part of muscle. 

Lean meat is the most concentrated and most easily digested 
of proteid foods, and therefore one of our most valuable articles 
of diet for building up the body and for repairing its tissues. 

Gluten. — Put some flour into a little muslin bag and pour 
water on it for several minutes. You will find that a gummy 
mass is left. That gummy mass is another form of proteid, 
and is called gluten. You eat gluten in bread, cake, and other 
articles of diet made from flour. 

Caseinogen. — This is one form of proteid in milk. Besides 
caseinogen, milk contains water, fat, milk-sugar, salts, and 
albumen; in other words, all the materials required for the 
nourishment of the human body. The proteids in milk build 
up the body and keep it in repair, while the fats and milk- 
sugar furnish fuel to give heat and power to do work. Milk is 
a perfect food for infants; but, for those who are older, it con- 
tains too much water and not enough proteid, sugar, and fats 
to be used as the sole article of diet in ordinary conditions of 
health. 

The curdling of milk.— The lining of the stomach in many 
animals, and especially in the young calf, contains a ferment 
called rennet. Rennet has long been used to curdle milk in 
making cheese. This ferment acts on the caseinogen and 
changes it into casein. The casein, while being formed in the 



18 PHYSIOLOGY FOR YOUNG PEOPLE 

milk, entangles the fat globules in its meshes; and these to- 
gether form the soft, semi-solid mass called the curd. The 
curd when pressed and dried forms cheese. The watery part 
that remains is called whey. It consists of a small amount of 
sugar, salts, and albumen, and a large amount of water. 

The souring of milk.— When milk is allowed to stand, 
germs act on the sugar that it contains and change the sugar 
into an acid which gives the milk a sour taste. The acid also 
changes the caseinogen into a soft curd. 

Contamination of milk. — Milk readily absorbs odors from 
decaying matters, from vegetables such as onions, and from 
other substances that have strong odors. These give rise to a 
disagreeable taste in the milk. 

The germs of such diseases as typhoid fever, scarlet fever, 
diphtheria, and tuberculosis may get into milk, and thus spread 
these diseases, if it is handled by persons that are recovering 
from, or have been exposed to, one of them. Another way 
these diseases are sometimes spread is by washing cans, pails, 
or other milk vessels in water that contains disease germs. 

Milk, like all other food, must be kept clean in order to be 
pure and wholesome. The stables, cows, and those who milk 
them should be clean. Pails, cans, and bottles used to hold 
milk should be thoroughly washed with lukewarm water and 
then scalded with pure boiling water each time they are used. 
Milk should be kept in a clean, dry, well-ventilated room that 
is free from strong odors, and at a temperature not higher than 
45° F. 



KINDS OF FOOD AND THEIB BSES 1!) 

Destroying germs in milk.— When milk is uncovered, 
germs of different kinds, or bacteria as they are also called, 
get into it with dust from the air. During the process of milking, 
a few bacteria will get into the milk even when the stables, 
cows, and those that milk them are as clean as possible. But 
a very much greater number of bacteria get into milk, along 
with dust, w T hen the stables, cows, and milkers are not clean. 
These bacteria increase in number very rapidly if the milk is 
allowed to remain warm. If, however, it is soon cooled down 
and kept at a temperature not higher than 45° F., the bacteria 
are unable to increase in number for a day or two. 

The bacteria in milk may be destroyed by heating the milk. 
If the temperature is not raised to the boiling point, the milk is 
said to be pasteurized. In the " Year-book of the Department 
of Agriculture" for 1907, issued by the Government of the 
United States, the following directions are given for pasteurizing 
milk: "Milk may be efficiently pasteurized in the household by 
setting the bottle of milk in a vessel containing water, and heat- 
ing the water until the milk reaches a temperature of about 
150°. It may then be removed from the stove and allowed to 
stand for twenty to twenty-five minutes. The temperature of 
the water will be above that of the milk, and while it slowly cools 
the milk will be thoroughly heated. It should then be chilled 
at once and kept cold until used." 

When milk is thus pasteurized, nearly all, if not all, the 
bacteria it contains are killed. But in the milk there are still 
spores, which correspond to the seeds of larger plants, and 



20 PHYSIOLOGY FOR YOUNG PEOPLE 

these may produce other bacteria. If the milk is now cooled 
to about 45° F., and kept cool, the spores in it cannot produce 
bacteria. Milk for infants should not be kept warm during 
the night. 

The bacteria in milk may be destroyed by simply heating it 
until it boils. But when milk is heated above 167° F. it loses 
some of its food value. If milk is boiled freely, it is changed 
considerably, and may cause serious intestinal troubles, es- 
pecially in children, if it is used for some time. 

Carbohydrates. — Such a word as carbohydrates does not 
mean much to you, but you are as well acquainted with exam- 
ples of carbohydrates as with the different proteids. Carbo- 
hydrates is but another name for starch and sugar. They 
contain carbon, oxygen, and hydrogen, but no nitrogen. Carbo- 
hydrate food furnishes heat and the power to work, and is 
sometimes called fuel food. 

Starch. — Starch forms a large part of all cereals, such as 
wheat, rye, corn, barley, rice, and oats. Potatoes contain a 
large amount of starch, and it is contained also in peas and 
beans, in arrowroot, tapioca, and sago. 

Starch is made up of tiny granules. When corn starch is 
rubbed between the fingers these little bodies have a gritty 
feeling. The form of the granules is different in each variety 
of starch, so that the different varieties may be distinguished 
from one another by looking at the granules with a micro- 
scope. 

Bread. — In this country bread is usually made from wheat 



KINDS OF FOOD AND THEIR USES 



21 



/ ^OOOOOOOOoOT 






^ 







flour. A grain of wheat is composed largely of starch and the 
proteid substance called gluten. The picture shows a section 
of a grain of wheat magnified. The outer layers are the bran, 
which resembles woody 
fibre. The row of large 
dark cells beneath this is 
composed of gluten. Be- 
neath the gluten are cells 
containing small round 
starch granules. 

When wheat is ground the 
outside layer of bran is 
peeled off and removed. 
Wheat flour consists of a 
large amount of starch and 
a much smaller amount of gluten. Bread is poor in fat. This 
deficiency is usually made good by the use of butter, which 
renders the bread more palatable. 

Meal, made from corn or oats, also contains much starch, a 
considerable amount of proteid matter, and some fat. 

Peas and beans. — Peas and beans contain starch and proteids. 
They are not so easily digested as meat or bread, yet on ac- 
count of their low cost and the amount of food substance in 
them, they may often be used to advantage in the place of 
higher-priced food. 

Sugar. — The ordinary sugar that we use for sweetening our 
food is called cane-sugar because it was first obtained from 



SECTION OF GRAIN OF WHEAT 

1. Bran. 2. Gluten cells. 3. Cells con- 
taining grains of starch 



22 PHYSIOLOGY FOR YOUNG PEOPLE 

sugar-cane. It is found also in the juice of many other plants. 
At present it is commonly made from sugar beets. It is espe- 
cially useful as a food in times of great exertion, because, 
being rapidly digested, it quickly reaches the muscles and 
supplies them with material for producing muscular power. 

The amount of sugar that may be eaten without bad effects 
depends much on the amount of active exercise that is taken. 
A person doing hard work in the open air can eat a good deal of 
sugar, while the same quantity would cause indigestion if taken 
when one is living an indoor life and taking little exercise. 

Milk contains from four to five per cent, of a form of sugar 
called milk-sugar. It is said to be the most digestible sugar 
for infants. 

Another variety of sugar is grape-sugar. It may be seen as 
yellowish granules in dried raisins, and is found in small quan- 
tities in other fruits. It is not so sweet as cane-sugar, and 
differs from it in appearance. 

Starch and sugar are closely related. The starch in fruits is 
changed into sugar as they ripen, and the starch in the food 
that we eat is changed into sugar as the food is digested. 

Fats. — Fats contain exactly the same materials as do the 
carbohydrates, viz., carbon, hydrogen, and oxygen : — but in 
different proportions. Fats are useful chiefly to furnish heat 
and power to work, and are found in animal food, such as 
meats, fish, and butter. They are abundant, too, in some 
vegetable products, such as olives and cotton-seed; and are 
contained in considerable quantities in such cereals as oats 



KINDS OF FOOD AND TIIKII! USES 



23 



and corn. In very cold countries the fats are valuable food- 

«/ 

Stuffs, because they can furnish an abundant supply of heat. 
The reason that the Eskimo would rather eat blubber than 
fruit is because the blubber supplies hjm with fat, and fruit 
does not. 

Butter. — The fat in fresh milk is in the form of very small 
globules, which are evenly 
distributed throughout the 
milk. If it is allowed to 
stand for some hours, these 
globules and some milk ad- 
hering to them rise to the 
surface because the fat is 
lighter than the rest of the 
milk. The part that rises 
to the surface is called 
cream. When cream that is 
cool is agitated in a churn, 
the little globules unite and 
form a solid mass called butter. The liquid that remains after 
the butter is removed is called buttermilk. Butter is an im- 
portant article of diet, for it furnishes the chief source of fat 
in the food of children and many grown people. Fat meat is 
also a valuable form of food, but many persons do not like it 
so well as butter. 

Nuts. — Nuts contain proteid, some starch, and a variable 
amount of fat. The cocoanut, chestnut, almond, and English 




ROUND PARTICLES OF FAT IN A DROP OF 
MILK SEEN UNDER A MICROSCOPE 



24 PHYSIOLOGY FOR YOUNG PEOPLE 

walnut are the varieties that contain the most nutriment, but 
some persons cannot digest them. Their chief value is to afford 
variety in the diet. 

Salts. — Salts are mineral food. You are familiar with the 
word salt as the name of common table salt. But this is only 
one kind of salt. There are, also, salts of lime, potash, phos- 
phorus, iron, and many others. Some salts are used to make 
bone tissue. Other salts cannot be used to build up tissue, 
or to furnish heat and muscular power, yet they help us to 
digest the articles of food that serve these purposes. The min- 
eral part of bones consists largely of salts of lime. 

Common table salt is an important article of food. It is 
found in considerable quantities in the blood and in all the 
other fluids of the body. It would not be possible to live with- 
out it as an article of diet. It stimulates the appetite and fur- 
nishes material required for the secretion of gastric juice, an 
important digestive juice of the stomach. Too much salt in 
the food produces thirst. Almost every kind of food that we 
eat contains some salt, so that we obtain a considerable supply 
of it in addition to what we add to our food. 

Mr. Henry W. Nevinson, in writing in Harper's Magazine, of 
that section of Africa called "The Hungry Country," says: 

"All living creatures in this region are crazy for salt. The 
natives will sell almost anything for it, and a pinch of it is a 
greater treat to a child than a whole bride-cake would be in 
England." Even the bees and the butterflies seek salt. Mr. 
Nevinson wrapped a bag of salt in tar paper and put it on the 



KINDS OF FOOD AND THEIR USES 25 

ground to see what the bees would do to it. Tn twenty minutes 
it was densely covered with bees. A little salt on a damp rag 
will attract butterflies until "the rag will be a blaze of colors, 
unless the bees come and drive the butterflies off." 

Green vegetables. — Green vegetables, such as cabbage, carrots, 
turnips, string beans, green peas, and the like contain much 
less carbohydrates and proteids than cereals do. But they are 
useful on account of the salts that they contain, and they fur- 
nish a pleasant variety in diet. 

Fruits in great variety are used for food. Their chief nourish- 
ing substances are the sugar and salts that they contain. 

Water. — Water, like salt, is a mineral food. Our blood, 
bones, muscles, and all other organs contain water. It is 
absolutely necessary not only to health, but to life. You could 
live without any other kind of food longer than without water. 
Most articles of diet contain it; some contain it in large quan- 
tities. For instance, beef is one-half water, potatoes are three- 
fourths water, and milk is about nine-tenths water. All solid 
food contains some water, and fluid food is largely composed 
of it. 

Since water is so necessary to mankind, a plentiful supply of 
pure drinking water is very important. Drinking water is 
usually taken from springs, wells, rivers, or lakes. Water that 
contains decaying animal or vegetable matter is not fit for use. 
Hence, water from shallow wells, or from wells near drains, 
farmyards, or cesspools is wholly unfit for drinking. 

The germs of such diseases as typhoid fever, cholera, and 



26 



PHYSIOLOGY FOR YOUNG PEOPLE 



dysentery are easily conveyed in drinking water. Every one 
living near the banks of streams or lakes from which drinking 
water is obtained should be extremely careful to preserve the 
purity of the water, and should never, under any circumstances, 




THE SURFACE SHOULD NOT SLOPE TOWARD THE WELL 

allow anything to be put into the water that can possibly con- 
taminate it. All wells should be fenced off, so that cattle and 
other domestic animals and fowls may be kept at a considerable 
distance from them. The site for a well should be chosen 
carefully, and should be a raised spot, so that the surface water 
will drain away from the well and not toward it. 

Whenever there is even a suspicion that the drinking water 
is not pure it should be boiled. The germs of disease are 
destroyed by boiling. 



KINDS OF FOOD AND THEIR USES 27 

Tea and '.coffer. — The value of tea and coffee is in their flavor 
and in their power mildly to stimulate the nervous system. 
Both are merely flavored water. Both furnish a means of 
relieving thirst and of introducing a needful amount of fluid 
into the body. Tea, when properly made and taken in reason- 
able quantity, may be considered healthful for many people, 
but it does not appear to be suitable to all. Excessive tea 
drinking, or the drinking of tea that is too strong, hinders diges- 
tion and disturbs the nervous system. 

Coffee should be made from newly roasted and ground beans. 
If the beans are ground too long before being used, much of the 
flavor is lost. The action of coffee is much like that of tea. 
There are many persons that prefer coffee because it aids 
digestion and affects them in every way more agreeably than 
tea does. Excessive quantities are harmful. 

Cocoa and chocolate. — Cocoa and chocolate are both prepared 
from the cacao bean. They contain some food substance in 
the form of fat, proteid, and starch. When properly prepared 
they are wholesome beverages, and furnish desirable hot drinks 
for children and young people. When tea, coffee, cocoa, or 
chocolate is made for children it should be made weaker and 
more milk should be added than when it is made for older 
persons. 

The railroads and alcoholic liquors.— The railroad com- 
panies of this country have for a long time had strict rules 
against the use of alcoholic liquors by their employees while on 
duty; and many companies give a preference, in filling positions, 



28 PHYSIOLOGY FOR YOUNG PEOPLE 

to men who are known not to drink such liquors. The purpose 
of these rules is to make the operating of the roads as safe as 
possible. 

It is evident from the rules quoted below that railroad com- 
panies, at least, consider that the use of alcoholic liquors un- 
fits employees for their best service. 

The Delaware, Lackawanna & Western Railroad Co. 
The use of intoxicating drinks on the road or about the premises 
of the Company is strictly forbidden. No one will be employed 
or continued in employment who is known to be in the habit of 
drinking intoxicating liquor. 

E. G. Russell, 

General Superintendent. 

Boston & Maine Railroad 
Intoxication, or the habitual use of intoxicating liquors by 
employees, is strictly forbidden, and will be sufficient cause for 
dismissal 'from the service of the road. Total abstinence in this 
particular is necessary to safety in operating the road, and em- 
ployees in any capacity who frequent gambling houses or places 
where liquor is sold, will not be retained in the service. 

D. W. Sanborn, 

General Superintendent 

Chicago, Milwaukee & St. Paul Railway Co. 
The use of intoxicating drinks has proven a most fruitful source 
of trouble to railways as well as to individuals. The Company will 
exercise the most rigid scrutiny in reference to the habits of em- 
ployees in this respect, and any employee who has been dismissed 
on this account will not be re-employed. Drinking when on duty 



KINDS OF FOOD AND THEIR USES 29 

or frequenting saloons will not be tolerated, and preference will 
be given to those who do not drink at all. 

H. R. Williams, 

General Manager. 

Southern Pacific Company 
The use of intoxicants by employees while on duty is prohibited. 
Their use, or the frequenting of places where they are sold, is suf- 
ficient cause for dismissal. 

Rock Island Lines 
Little Rock, Ark., January 11, 1909. 

Dear Sir: — Replying to yours of January 5th, our rules are as 
follows : 

"The use of intoxicants by employees while on duty is prohibited. 
Their habitual use, or the frequenting of places where they are sold, 
is sufficient cause for dismissal/' 

"The use of tobacco by employees when on duty in or about 
passenger stations, or on passenger cars, is prohibited. " 

In their applications for employment, applicants are requested 
to state whether or not they smoke cigarettes; if so, we do not 
employ them. We also forbid the smoking of cigarettes by the 
employees of any department while on duty. 

Trusting this information may be of some benefit to you, I 

remain, __ J ' 

Yours truly, 

F. J. Easley, 

Superintendent. 

SUMMARY 

1. Food substances consist of proteids, carbohydrates, fats, water, and 
salts. 

2. The proteids are needed to replace worn-out particles of the cells, 
and to build up new tissue. 



30 PHYSIOLOGY FOR YOUNG PEOPLE 

3. Some of the common proteids are albumen, myosin, gluten, and 
caseinogen. 

4. To prevent bacteria from increasing in number in milk, it should be 
cooled as soon as possible to 45° F., and kept cool until it is used. 

5. To destroy bacteria in milk it should be kept at 160° F. for twenty 
minutes. It should then be kept cool to prevent spores from producing 
other bacteria. 

6. Carbohydrates consist of starch and sugar. 

7. They furnish material for producing heat and power to work. 

8. Fats, too, are used in the body to produce heat and power to work. 

9. When cream is churned the little globules of fat it contains unite 
and form butter. 

10. The mineral part of bone, which makes it hard and firm, consists 
chiefly of salts of lime. 

11. Water may convey disease germs. 

12. These germs may be destroyed by boiling the water. 



CHAPTER III 
COOKING 

Why we cook our food. — One reason why we cook food is 
to make it more digestible. While meat is cooking, the con- 
nective tissue, which binds the muscle fibres together, is softened 
and dissolved so that the fibres fall asunder and can be more 
easily digested. When lumps of meat are swallowed, gastric 
juice can attack and digest the fibres on the surface only, for it 
cannot reach those in the centre. The central part of a tough 
piece of meat that is swallowed without being thoroughly mas- 
ticated is digested slowly and with difficulty, or may remain 
undigested. The granules of starch in cereals are contained 
in tough envelopes of a material called cellulose. During the 
process of cooking the starch granules swell up and burst their 
envelopes. For this reason, cooked starch is digested more 
completely and more quickly than raw starch. 

Another reason for cooking food is to destroy parasites and 
germs that may be present in the raw food. These are de- 
stroyed when the temperature is raised to the boiling point. 

The cooking of food develops a flavor in it so that it will taste 

better. The taste or even the smell of a savory dish is sufficient 

to excite a flow of saliva and gastric juice, and thus aid diges- 

31 



32 PHYSIOLOGY FOR YOUNG PEOPLE 

tion; whereas unsavory or carelessly prepared food has the 
opposite effect. 

The methods of cooking in common use are boiling, stewing, 
roasting, baking, broiling, frying, and steaming. 

Boiling. — When meat is put into water that is boiling, the 
albumen on the surface is seared, or hardened, in a few minutes. 
A thin layer is thus formed on the surface. 

Within this seared layer the juices are held imprisoned so 
that, even after the meat has been finally cooked through and 
through, it remains juicy, has lost but little of its nutriment, 
and has a fine flavor. After boiling for ten minutes the tem- 
perature of the water should fall slightly below the boiling point. 
If the water is kept at the boiling point for an hour or more the 
albumen in the inside will be overcooked and the meat will be 
tough and stringy. The temperature, however, should be only 
a little below the boiling point, or the inside of the meat will 
not be thoroughly cooked. 

Stewing. — Stewing differs from boiling. The object in 
boiling is to retain the juices in the meat. The object in stew- 
ing is to cook the meat at a temperature below the boiling point, 
so as to allow the juices to pass out into the water in which the 
meat is cooked. The best temperature for stewing is 180° F. 

If the meat to be stewed is cut up into small pieces the juices 
pass out more readily. The flavor may be changed by adding 
barley or sliced vegetables. When the solid portions of the 
meat and vegetables are eaten along with the liquid, the stew 
forms a wholesome, nourishing, and economical food. 



COOKING 33 

Soup. — Meat soups are made by cooking meat at a low tem- 
perature for five or six hours. The cheaper parts of meat are 
as well suited for making soups as the more expensive cuts. 
The food value is increased by cooking fragments of bone along 
with the meat. By long-continued cooking at a low tempera- 
ture the connective tissue of the meat is changed into gelatin 
and is gradually dissolved out into the water, along with 
the valuable juices, salts, and flavoring matter. Vegetables 
may be used alone for making soup, or they may be added to 
meat. 

Soup, as a rule, contains only a small amount of nourishment, 
but it increases the flow of gastric juice in the stomach. In 
this way it increases the appetite and aids in the digestion of 
the solid parts of the meal. 

Beef tea. — Beef tea and other similar extracts of meat con- 
tain only a small amount of food. They are valuable chiefly 
in the diet of invalids and others that are unable to take the 
usual amount of solid food. 

In making beef tea the meat should be cut up into very small 
pieces and put into cold water. One pound of lean meat is 
enough for one pint of water. The meat should stand in cold 
water for about an hour, and then be heated slowly in a double 
boiler, with occasional stirring. During this time the tempera- 
ture of the mixture should remain a little below 167° F., for, at 
this heat, proteid coagulates. After the mixture has been cook- 
ing at a low temperature for an hour, it should be heated to the 
boiling point and then removed from the fire. The tea should 



34 PHYSIOLOGY FOR YOUNG PEOPLE 

be poured from the meat and allowed to cool. When it is cool, 
the fat on the top should be removed. The tea will then con- 
sist of a brown liquid at the top and small particles of coagulated 
proteid below. If beef tea is boiled for some time the coagu- 
lated proteid becomes hard and difficult to digest. When the 
tea is boiled a scum is formed of coagulated proteid; and, if 
this is thrown away, the remaining part is of little value. 

Baking and roasting.— The old way, and by far the best 
way, to roast food wa^ to hang it on a spit over an open fire. 
In some countries this method is still employed for roasting, 
but it is not in use in the United States. What we call roasting 
is really baking. What we call roast beef is really baked beef. 
Baked beef is cooked in an oven instead of over the open fire. 
The oven should be very hot when the roast is put into it. The 
outer layers of proteid then form a coating on the surface, which 
keeps almost all the natural juices of the meat from passing 
out. A little of the juice, however, always escapes, and this, 
together with the melted fat, forms the gravy, which is very 
nutritious and may be used for basting the roast so as to pre- 
vent drying or burning on the surface. After ten or fifteen 
minutes the heat of the oven may be slightly reduced so as to 
avoid charring the surface of the roast. Meat, bread, cake, and 
many kinds of vegetables can be baked. 

In making bread, flour is mixed with yeast, salt, and water, 
and kneaded into a dough. If the dough is kept warm, little 
ferments in the flour act on the starch, which is, in part, changed 
to sugar. The yeast then attacks the sugar, and by a process 



COOKING 35 

called fermentation, forms alcohol and a gas known as carbon 
dioxide. Gluten is sticky when moist and prevents the carbon 
dioxide from passing off as soon as it is formed. This gas, in 
its efforts to escape, forms bubbles and causes the bread, or 
dough, to rise and become light and spongy. It is then baked 
in a hot oven. The heat destroys the yeast, stops fermenta- 
tion, and drives off all the alcohol. Baking powder may be 
used instead of yeast. 

Broiling. — Broiling is a method of cooking meat by bringing 
its surfaces near a glowing fire. Much less time is required for 
broiling than for roasting or boiling. Care should be taken to 
have the fire very hot, and the surface of the meat- should be 
placed near the fire. 

Steaks or chops intended for broiling should be cut thick. 
Thin pieces of meat become dry, shrivelled, and tough by broil- 
ing; but thick slices, when properly broiled over a very hot 
fire, are juicy, tender, and palatable. 

Frying. — Frying is a method of cooking in melted fat. The 
fat should be hot enough to harden the outer layer quickly and 
form a crust on the surface, so as to prevent the escape of the 
juices and to keep the fat from soaking in. Food that has 
soaked in much fat is very indigestible. The best frying is 
done by having the fat very hot and deep enough to cover the 
food, so that it becomes crusted all over at once. Then the fat 
cannot soak into it. 

Steaming. — Steaming is suitable for puddings, cereals, and 
many green vegetables. The cooking is done in a steamer or 



36 PHYSIOLOGY FOR YOUNG PEOPLE 

double-boiler, by the heat of steam that surrounds the vessel 
holding the food. 

What to eat. — As milk is composed of proteid, sugar, fat, 
salts, and water, it is a complete mixed diet. The proportion of 
water, however, is too great to allow it to be the sole food of an 
adult, but it is one of the best articles of diet for infants and 
children. Cream, too, is nourishing. It may be mixed with 
milk and used with oatmeal and other cereals, with bread, and 
with mashed potatoes, or in other ways. 

Children require fat in their food. They do not, as a rule, 
digest fat meat as well as grown people do. Butter is a very 
useful and agreeable form of fat, and is relished by almost 
every one. It is generally advisable to allow children to eat all 
the butter they want with bread, potatoes, or other food. 

Eggs are less quickly digested when fried or hard boiled 
than they are when poached, soft boiled, or made into custard. 
Since many persons soon tire of them, it is better not to have 
them every day. 

Roast beef, roast lamb, lamb or mutton chops, beefsteak, 
chicken, turkey, or fresh fish, at least once a day, are good for 
every one in ordinary health. 

Potatoes contain a large amount of water and starch, but are 
deficient in proteid. Although there is not much nourishment 
in them, they are easily digested. Their value as food is in- 
creased when they are eaten with butter, cream, or meat gravy. 
Because of the greater heat to which potatoes are subjected 
when they are baked in their skins, they are more mealy 



COOKING 37 

than when cooked in any other way, and so are more easily 
digested. 

Other desirable vegetables are green peas, string beans, baked 
beans, spinach, stewed celery, and asparagus. 

Rice, tapioca, and sago puddings are easily digested and 
wholesome. 

Pork of any kind, salted meats, salted fish, veal, liver, kidney, 
goose, and duck are hard to digest. Green corn, radishes, raw 
celery, onions, tomatoes, carrots, and cucumbers are not easily 
digested, and contain only a small amount of nourishment. 
Hot bread, hot buns and rolls are hard to digest, and so are all 
cakes that contain dried fruits. Pies, tarts, pastry, nuts, candies, 
and salads are not easily digested, and should be eaten only in 
small quantities. Green or partly decayed fruit should never 
be eaten. Dried, canned, and preserved fruits and jellies are 
not so desirable as fresh, ripe fruit. It should not be under- 
stood that these articles of food are here condemned as unfit to 
eat. Many persons find them useful, nourishing foods; others 
find that they must refrain from the use of some of them. On 
the whole, these articles should not form so large a part of our 
diet as those mentioned in the desirable list. 

How much to eat. — The amount of food, as well as the kind 
of food that one should eat, varies according to climate, occupa- 
tion, and habits. Boys and girls need more food in proportion 
to their size than grown people do ; for boys and girls must have 
material for growth as well as for repair of the tissues. People 
in cold climates need more heat-producing food than do people 



38 PHYSIOLOGY FOR YOUNG PEOPLE 

in warm climates. Men that work hard in the open air need 
more food than men that work indoors. 

Overeating. — The eating of an excessive amount of food 
at one or two meals may not cause very serious results, but con- 
tinued overindulgence in eating is sure to lay the foundation of 
disease. There is a limit to the amount of food that can be 
digested in a given time. If too much food is eaten, it may not 
be properly digested in the stomach and the intestine. Fer- 
mentation and decomposition may then take place and give 
rise to acute indigestion or other trouble. 

On the other hand, if an excessive amount of food is digested 
and taken into the blood, it will contain more food than the 
body needs. Part of this surplus food may be stored up in the 
tissues as fat. Part of it may be carried off through the liver 
and kidneys, and these organs will be overworked in their 
effort to get rid of the unnecessary food that was eaten. Many 
of the ills of the body arise from intemperate eating. 

How much water to drink. — Water is taken either as plain 
water, or in the form of soups, or beverages, which consist 
largely of flavored water. It is probable that many persons 
do not drink enough water. The average healthy adult re- 
quires about a quart and a half or two quarts of water every 
twenty-four hours. The amount varies with the season; for 
more water is required in hot than in cool weather, because of 
the greater loss of water from the body by perspiration. It is 
a good plan to drink one or two tumblerfuls of moderately cold 
water on rising in the morning, and smaller amounts at inter- 



COOK IXC 39 

vals during the (lay. One effect of cold water is to strengthen 

the muscles in the walls of the stomach and the intestine, and 
so enable them to do their work better. 

Water enters the blood from the intestine. The presence in 
the blood of a sufficient amount of water makes it easier for 
the cells of the tissues to obtain food from the blood, and also 
to get rid of the waste matter that is continually being formed 
in them. 

The drinking of very large amounts of water during, or im- 
mediately after, meals hinders digestion by diluting the gastric 
juice of the stomach and by overdistending that organ. The 
presence in the blood of too much water gives the heart too 
much work to do, and may be a cause of great danger if the 
heart or blood tubes are weak. 

Cleanliness and food. — Great care should be taken to keep 
food clean. Food that is exposed for sale should be kept under 
glass, or should be otherwise protected from flies and from dust 
that is raised by wind or passing vehicles. The kitchen is, in 
many respects, the most important room in a house. Its walls, 
floors, and utensils should always be kept clean. Food should 
be kept covered in order to protect it from flies and other animals 
that convey germs of disease. Table refuse should be burned 
or should be promptly disposed of in some other way. 

Flies. — The action of flies in spreading disease has only re- 
cently been fully recognized. Flies feed on all kinds of filth. 
Some of it adheres to their feet and other parts of their bodies. 
They may subsequently alight on meat, bread, or other food, or 



40 PHYSIOLOGY FOR YOUNG PEOPLE 

fall into milk. In this way flies often deposit germs on food, 
and so spread contagious disease. 

Flies should be kept out of the house. Windows and doors 
should be screened; and those that manage to get in should be 
killed by burning pyrethrum powder in the room, or in some 
other manner. Special care should be taken to keep flies from 
the kitchen, dining-room, and also from the sick-room if any 
one is ill with contagious disease. The number of flies would 
be greatly reduced if all kinds of filth both within and without 
the house were removed. Where everything is clean there are 
few flies. 

Meal time. — Our meals should be at the same hours every day, 
and far enough apart to give regular intervals of rest for the 
stomach between meals. The stomach requires rest, if it is to 
keep in a healthy condition. In this country most people eat 
three times a day. Fruit, cereal, and eggs make an easily 
digested breakfast that is suited to most people. Bread and 
butter, meat, some vegetables, and a light pudding form a 
wholesome midday, or evening, dinner. Luncheon or supper, 
should be of simple and wholesome articles of diet. We must 
remember that the real purposes of eating are much more im- 
portant than the pleasing of our palates. We eat to live, to 
grow, to keep warm, to have power, so that we may run, work, 
play, and think. 

Rules for eating. — Here are a few simple rules in regard to 
eating, which should always be observed: 

1. Eat slowly and chew the food well, so that it may become 



COOK IXC 41 

well mixed with the saliva, and that there may be time for the 
saliva to act upon the starch which the food contains. When 
food is well separated and torn apart the gastric juice acts upon 
it more readily! 

2. Stop eating as soon as you feel that your appetite is satis- 
fied. The stomach acts best when it is about two-thirds full. 

3. Take your meals at regular hours. The stomach requires 
a period of rest after the work of digesting a meal in order to 
make gastric juice for the next meal. 

4. Do not eat between meals. 

5. Supper, for children, should be the simplest and plainest 
meal of the day. 

6. Do not drink while you have food in your mouth. Saliva 
mixes more readily w r ith dry food. 

7. Never drink ice water at meal times, or for two hours 
after a meal. Gastric juice is most active when the contents of 
the stomach are at or near the temperature of the body. A 
low temperature like that of ice w r ater retards the action of 
gastric juice. 

8. Do not drink cold water freely when the body is overheated. 

9. Do not eat a hearty meal when very tired or very warm. 

10. Rest, if possible, for at least half an hour after a hearty 
meal, in order that the stomach may have a better chance to 
do its work. 

SUMMARY 

1. Cooking makes meat and starch more digestible. 

2. Cooking destroys parasites, and develops a flavor in food. 



42 PHYSIOLOGY FOR YOUNG PEOPLE 

3. When meat is boiled or roasted it should be subjected to the greatest 
heat at first. 

4. In making a stew or a soup with meat, the temperature should be 
kept low. 

5. In frying, the fat should be very hot before anything is put into it to be 
cooked. 

6. Potatoes are most easily digested when baked. 

7. Articles of food that are digested with difficulty should be avoided. 

8. Food should be kept clean, and should be covered to protect it from 
flies. 

9. Flies convey germs and often spread contagious disease. 

10. Meals should be at regular hours. The stomach needs an interval 
of rest between meals. 

11. A few established rules for eating should be observed. 



CHAPTER IV 
DRINKS WHICH CONTAIN ALCOHOL 

Many kinds of beverages containing alcohol are made in 
different parts of the world. These drinks differ from each 
other because they are made from different materials, and are 
prepared in different ways. Such beverages are known as 
wines of different kinds, beer and other malt liquors, whiskey 
and other distilled liquors. 

Fermentation. — When the juice of apples, or other fruit, is 
exposed to the air at ordinary temperatures, bubbles of gas, 
called carbon dioxide, soon appear and rise to the surface, and 
at the same time alcohol is formed. The same thing takes place 
if yeast is added to a solution of sugar and water. The process 
by which sugar in a solution is changed into alcohol and carbon 
dioxide is called fermentation. 

There are many varieties of fermentation. It is because of 
fermentation that wood, fruits, and other vegetables decay, that 
meats putrefy, and that sweet milk becomes sour. Milk be- 
coines sour because tiny bodies, called ferments, enter it and 
change the sugar of the milk into lactic acid, which gives the 
milk a sour taste. If all the ferments could be kept out of 
milk it would not turn sour for months, or even years. 

Fruit may be kept for a long time if it is first boiled and then 

put into air-tight vessels. The ferments that fall upon the fruit 

43 



44 



PHYSIOLOGY FOR YOUNG PEOPLE 




YEAST CELLS 

Before budding. 2. Budding to 
form more cells 



from the air are killed by boiling, and fresh ones cannot enter 
vessels that are air-tight. Meat and vegetables are often pre- 
served from decay in a similar manner. 

Fermentation of this kind is always caused by the action of 

tiny bodies which exist almost 
everywhere, and belong to the 
lowest order of plant life. These 
bodies are so small that we can 
see them only with the aid of a 
microscope, and for this reason 
they are sometimes called micro- 
organisms. They are called fer- 
ments because they cause fermentation. 

Fermentation by which alcohol is formed in liquids contain- 
ing sugar is caused by a ferment called the yeast plant. Each 
of these tiny plants consists of a single cell. In the picture the 
yeast plants are magnified. No. 1 shows single isolated cells or 
plants. No. 2 shows cells that are budding to form new plants. 
The spores of these plants correspond to the seeds of larger 
plants, and they float about in the air. Some spores drop into 
the fresh juice when wine or cider is being made and cause 
fermentation. The ferment, as it grows, takes nourishment 
from the sugar in the juice, and this so changes the sugar that 
alcohol and carbon dioxide are formed from it. The carbon 
dioxide comes up in bubbles to the surface of the juice and 
passes into the surrounding air, while the alcohol remains behind 
in the juice. 



DRINKS WHICH CONTAIN ALCOHOL 



45 



Wine. — The term wine is generally used to mean the fer- 
mented juice of grapes, but wine is made also from the juice 
of other fruits, such as currants, pears, cherries, and black- 
berries. 

Grapes and other fruits contain no alcohol because the fer- 
ments remain on the skin, or outer part, and cannot enter the 
fruit to act on the sugar that forms in the fruit as it ripens. 
The fresh juice of all kinds of fruit consists chiefly of water and 
sugar, and is therefore harmless; but it remains so for only a 
short time. At the ordinary temperature that prevails at the 
time of the year when fruits ripen, ferments that get into the 
juice soon begin to grow and cause 
fermentation. The sugar in the 
juice is changed, and alcohol and 
carbon dioxide are produced. Ordi- 
nary wines contain from six to 
eleven per cent, of alcohol, but 
some contain even more. 

Cider. — Sweet cider ferments 
rapidly at a suitable temperature, 
and the sugar it contains is changed, 
forming alcohol and carbon dioxide. 
The amount of alcohol in cider de- 
pends upon the amount of fer- 
mentation that has taken place. The alcohol in cider varies 
from a fraction of one per cent, to about eight per cent. 
Cider is considered by many to be a harmless drink, but it is 



; 



FERMENTATION IN A GLASS 
OF CIDER 



46 PHYSIOLOGY FOR YOUNG PEOPLE 

not. for even what is sold as sweet cider often contains more 
alcohol than average beer. 

Malt liquors. — Beer, ale, and porter are made from grain, 
generally from barley. The grain is first moistened and kept 
in a warm place until it sprouts, in order to change its starch 
into sugar. Then the grain, or malt as it is now called, is dried 
and ground, and the sugar is dissolved out with water. This 
is boiled with hops to give it a bitter flavor, and yeast is added 
to cause fermentation and produce alcohol from the sugar. 
The amount of alcohol in beer and other malt liquors varies 
from one to about nine per cent. 

Distilled liquors. — When wine or malt liquor is heated suf- 
ficiently, the alcohol in it is changed into steam, or vapor, which 
rises and passes off from the liquor. Part of the water also in the 
liquor passes off as vapor along with the alcohol, but much of the 
water remains behind because alcohol boils at a temperature of 
170° F., while water boils at a temperature of 212° F. If the 
vapor is collected and allowed to cool, it quickly changes back to 
a liquid which contains a greater proportion of alcohol than the 
wine or malt liquor. This process is called distillation. The 
more common distilled liquors are whiskey, brandy, rum, and gin. 

Brandy is made by heating wine. As the vapor passes off 
it is collected and cooled. The new liquid, which is called 
brandy, contains more alcohol and less water than wine. 

Whiskey and gin are made from starch obtained from grain 
or from potatoes. The starch is first changed to sugar, water 
is added to dissolve the sugar, and alcohol is formed by fer- 



DRINKS WHICH CONTAIN ALCOHOL 47 

mentation, as in making beer. The liquid is then distilled. 
Whiskey, like brandy, is made up mainly of alcohol and water 
in about equal parts. 

In making rum, water is added to molasses. This liquid is 
then fermented and distilled. The new liquid, which is called 
rum, contains a large amount of alcohol. 

It is well known that Abraham Lincoln was a total abstainer 
from the use of alcoholic liquors, and that he urged others to 
abstain from drinking them. He is said to have composed 
and advocated the following pledge: 

" Whereas, the use of alcoholic liquors as a beverage is pro- 
ductive of pauperism, degradation, and crime, and, believing 
it is our duty to discourage that which produces more evil than 
good, w 7 e therefore pledge ourselves to abstain from the use 
of alcoholic liquors as a beverage." 

The following account is given of Lincoln's reception of the 
committee that came to notify him that he was nominated for 
the office of President in 1860: 

"Mr. C. C. Coffin, a most distinguished journalist of the day, 
who accompanied the notification committee from the Chicago 
Convention to Springfield, at the time of Lincoln's first nomina- 
tion for the Presidency of the United States, related in his news- 
paper a few days later an incident that occurred on that occa- 
sion. He says that, after the exchange of formalities, Lincoln 
said: 'Mrs. Lincoln will be pleased to see you, gentlemen. 
You must be thirsty after your long ride. You will find a 
pitcher of water in the library.' 



48 PHYSIOLOGY FOR YOUNG PEOPLE 

" There was a humor in the invitation to take a glass of water, 
which was explained to Mr. Coffin by a citizen of Springfield, 
who said that, when it was known that the committee was com- 
ing, several citizens called upon Mr. Lincoln and informed him 
that some entertainment must be provided. 

"'Yes, that is so. What ought to be done? Just let me 
know and I will attend to it/ he said. 

" l Oh, we will supply the needful liquors/ said his friends. . 

(li Gentlemen/ said Mr. Lincoln, 'I thank you for your kind 
attention, but must respectfully decline your offer. I have no 
liquors in my house, and have never been in the habit of enter- 
taining my friends in that way. I cannot permit my friends to 
do for me what I would not myself do. I shall provide cold 
water — nothing else/" 

SUMMARY 

1. When a solution containing sugar ferments, alcohol and carbon di- 
oxide are formed from the sugar. 

2. The juice of apples, grapes, and other fruits contains sugar, and 
alcohol may be formed from any of them. 

3. Alcohol may be made from grain. It is allowed to sprout so as to 
change part of its starch to sugar. 

4. When steam from a heated liquid is collected and cooled down to a 
liquid again, the process is called distillation. 

5. Distilled liquors contain more alcohol than wine or malt liquors. 



PART II— THE FUNCTION OF NUTRITION 

CHAPTER V 

PLANT NUTRITION 

Food as a fuel. — When you see a steam-engine drawing a 
train, you know that it is using up fuel, and that more fuel will 
be needed from time to time to take the place of what is being 
consumed. And you know that if the supply of fuel should 
give out, the engine would soon stop and be unable to do any 
more work until it got a new supply. 

In this respect, at least, living things, both plants and ani- 
mals, are like an engine. When a plant or an animal works, 
you may be sure that it is using up fuel. Plants perform 
different kinds of work. They grow, move, and make leaves, 
flowers, fruit, and seeds. Animals, also, grow, . move, build 
homes, seek food, and do many other kinds of work. The fuel 
which plants and animals use we call food. 

An engine has a fire-box, and the fuel is all consumed in it. 
In plants and animals the food is not consumed in one place. 
Plants and animals, as you have already learned, are made up 
of little cells, and each cell consumes its own supply of food. 

The coal consumed in an engine produces heat, and also the 
power that enables the engine to do work. An engine, how- 
ever, cannot use the coal to repair itself as its parts wear out. 

49 



50 



PHYSIOLOGY FOR YOUNG PEOPLE 




As food is consumed in the plant or the animal cell, heat and 
the power to grow and do other kinds of work are produced, 
and, in addition, the cell uses the food to 
make good the loss of its own cell-sub- 
stance that is constantly wasting away. 
The process of using food for all these 
purposes is called nutrition. 

Plants as manufacturers. — Mosl 
plants, i. e., all green plants, have the 
power to manufacture their food from 
raw material. Animals cannot do this. 
It is commonly said that plants obtain 
their food from the soil through their roots 
and from the air through their leaves, but 
the fact is that a plant obtains from the 
soil and the air only materials out of 
which it makes its food. Near the tips of 
the roots of plants are root-hairs, each of 
which is a prolongation of the wall of a 
cell on the surface of the root. Through 
these root-hairs, or long cells, plants take from the soil water, 
which passes up through the body of the plant to its leaves 
In this water are dissolved mineral substances that the plant 
uses in making food. On the under surfaces of leaves are 
many thousands of little openings called pores. Through these 
pores plants take from the air a gas called carbon dioxide, 
which they use in making food. 



PLANTS WITH THEIR 
ROOT-HAIRS 

1. Without dirt adhering 
to the hairs. 2. With 
dirt adhering to the hairs 



PLANT NUTRITION 



51 



Water consists of a union of two gases, hydrogen and oxygen; 
carbon dioxide consists of a union of carbon and oxygen; starch 
consists of a union of carbon, hydrogen, and oxygen. Now, a 
chemist can separate water into hydrogen and oxygen, and 
carbon dioxide into carbon and oxygen. He knows how much 
carbon, hydrogen, and oxygen are needed to make starch; yet 
in his workshop he cannot put them together so as to make 
starch. But every green 
plant can do it. The green 
coloring matter in the leaf 
of the plant absorbs sun- 
light. The leaf -cells obtain 
from this sunlight the 
power to separate the hy- 
drogen and oxygen of 
water, the carbon and oxy- 
gen of carbon dioxide, and 
to put together all of the 
carbon, all of the hydrogen, 
and some of the oxygen. 
Thus the leaf-cells make 
starch which the plant 
needs for food. The oxy- 
gen that the cells do not 
use goes out into the air. 

Plants need, however, other kinds of food in addition to 
starch. These the green plants make by combining with the 




SECTION OF LEAF SHOWING TWO PORES, 
P. P., ON UNDER SURFACE 



52 PHYSIOLOGY FOR YOUNG PEOPLE 

materials contained in starch other materials, such as nitrogen, 
sulphur, and phosphorus. Plants obtain these, through their 
root-hairs, from water in the soil. Out of these materials they 
manufacture all the food that is needed to produce growth, 
repair waste, and do all of their other work. 

Much of the food manufactured by the plant is insoluble (i. e., 
cannot be dissolved) in sap, as the water in the plant is called; 
but the plant can change this food so that it is soluble in sap. 
When the food is dissolved it flows in the sap to the cells in all 
parts of the plant. As it is needed, the food then passes through 
the cell walls into the cells, and is there used up by the proto- 
plasm. Now, this dissolving of food so that it can be carried 
by the sap * and taken into the plant cells is similar to the 
digestion of food by animals. For, in the process of digestion 
in animals, the food is dissolved so that it can be distributed 
to the cells. 

Green plants both manufacture and digest their food; other 
plants and animals can only digest food, they cannot manu- 
facture it. All living things, therefore, both plants and ani- 
mals, depend for their nourishment on this power of green 
plants to manufacture food from raw materials obtained from 
the soil and from the air; for some animals, the herbivorous 
ones, feed directly on plants, while others, the carnivorous 
ones, feed indirectly on plants by feeding on animals that feed 
on plants. 

Oxidation in plants. — When you are starting a fire in a 
stove you keep the damper and the lower door open, so that 



PLANT NUTRITION 53 

air may get to the fire; and, if the fire seems about to go out, 
you blow or fan it gently, so as to give it a greater supply of 
air. Air contains oxygen, which unites with the wood or coal 
in the act of burning. This uniting of oxygen with wood or 
coal is often called combustion, or oxidation. In the case of 
wood or coal, oxidation is so rapid that light is produced, as 
well as heat and power. Like the fire, plants must have air 
so that oxygen from the air may unite with food in the cells 
and furnish heat and the power to work. Oxidation in the 
cells of plants takes place more slowly than the combustion in 
a stove, and therefore light is not produced. 

In the body of a plant there are spaces between the cells. 
These spaces form continuous passages throughout the plant 
body and connect with the air by means of openings, or pores, 
at the surface. The pores are very numerous on the under 
side of the leaf, and there are also pores through the bark. 
When oxygen from the air .has entered through the pores into 
the air-spaces, it passes on through the cell walls into the cells, 
and is there used by the protoplasm in oxidizing the food. 

When food is oxidized in the cell, waste matter is produced 
which the cell must get rid of. This waste matter consists 
largely of carbon dioxide, and water in the form of vapor. 
These pass through the cell wall into the spaces between the 
cells and out of the plant through the pores on the surface. 

This escape of carbon dioxide through the pores of the leaf 
can best be observed at night, when the leaf is not absorbing 
carbon dioxide from the air. During the daytime, carbon di- 



54 PHYSIOLOGY FOR YOUNG PEOPLE 

oxide that is given off from the cells as waste matter mingles 
in the leaf with that absorbed from the air, and is used in 
making starch. 

SUMMARY 

1. When an engine, a plant, or an animal does work it uses up fuel. 

2. Green plants manufacture food from raw materials obtained from 
the air and the soil. 

3. They take in raw material through root-hairs and pores in their 
leaves. 

4. Green plants make starch in their leaves from carbon dioxide and 
water. 

5. To the materials used in making starch, green plants add other 
materials to make proteids and oils. 

6. Green plants digest food after they manufacture it. 

7. Animals and other plants digest food, but cannot manufacture it. 
They depend upon green plants for food. 

8. Plants take in oxygen and oxidize food in their cells. 




AN AMCEBA 



CHAPTER VI 
ANIMAL NUTRITION 

The simplest kind of animal nutrition.— In an earlier 
chapter you learned something about the tiny animal called the 
amoeba, which consists of a single cell. It consists of proto- 
plasm without any covering, or skin, so it 
does not need any mouth. It can send out 

at any point a little projection that creeps / fllp^ip|f * 

around a food particle — consisting usually 
of a tiny plant — and encloses it, together 
with a little water. When the food particle 
and the water are enclosed within the body of the amoeba, a 
fluid, which the little animal makes, dissolves, that is digests, 
at least part of the food. The part that is dissolved is taken 
up by the protoplasm and used in repairing waste and in pro- 
ducing heat and the power to work. The part of the food 
material that cannot be dissolved may be given off at any 
point from the surface of the amoeba. The type of nutrition 
in the amoeba is the simplest kind of animal nutrition. 

The jelly-fish. — A jelly-fish is higher in the scale of animal 
life than an amoeba and shows a more advanced type of nutri- 
tion. In the jelly-fish shown in the picture there is a mouth 

55 



56 



PHYSIOLOGY FOR YOUNG PEOPLE 




A JELLY-FISH 



on the under surface of 
the umbrella, and above 
the mouth there is a 
sac - like stomach. A 
long arm extends down- 
ward from each of the 
four corners of the 
mouth. As tiny ani- 
mals in the water drift 
against these arms they 
are paralyzed or killed 
by stinging cells, and 
are afterward drawn 
into the mouth and the 
stomach. The part of the food that cannot be digested is 
cast out later through the mouth; but the part that has been 
digested is conveyed to all parts of the body by little tubes that 
run out from the stomach in all directions. In these animals 
the food that is used 
up in the cells comes 
to them directly from 
the stomach. 

The earthworm.— 
The common earth- 
worm is higher in the 
scale of animal life 

SECTION OF JELLY-FISH 
than the jelly-fish, and, (m) Mouth. GO Stomach. (c)Tube 




ANIMAL NUTRITION 



57 



accordingly, shows a still more advanced type of nutrition. A 
straight tube, called the alimentary canal, extends from one 
end of its body to the other. Food mate- 
rial, or soil containing food material, is taken 
in at the mouth, which is the beginning of 
the alimentary canal. This food material on 
its way along the canal passes into the part 
called the esophagus, and then enters 
another part called the gizzard. The giz- 
zard has a thick muscular wall lined with 
a horny membrane. In this part of the 
canal the food material is rolled about and 
ground fine to get it ready for digestion. 
On leaving the gizzard the food material 
passes into a part of the canal that has a thin 
wall. Cells in the wall of this part secrete a 
fluid that digests the food material that can 
be digested. The indigestible part passes on 
and leaves the alimentary canal through an 
opening at its end. 

The simplest type of blood circulation.— 
The cells of the body of the earthworm do 
not receive digested food directly from the 
alimentary canal, as in the jelly-fish. The food that has been 
digested passes through a thin membrane into little blood tubes 
in the wall of the canal, and then along blood tubes to all 
parts of the body. The earthworm has no heart, but blood is 




ALIMENTARY 
CANAL OF 
EARTHWORM 

(For blood tubes, see 
chap. xvi. p. 224) 



58 PHYSIOLOGY FOR YOUNG PEOPLE 

forced to all parts of the body by muscles in the walls of the 
larger blood tubes, and the cells get their food from the blood. 

Higher types of nutrition and circulation.— The plan, as 
seen in the earthworm, of an alimentary canal for digesting 
food, and of a system of blood tubes for distributing digested 
food to the cells, is found in all higher animals. But the supply 
of food needed by larger and more active animals is so much 
greater than the supply needed by the small, sluggish earth- 
worm that an alimentary canal consisting of a straight tube 
would not digest enough food for them. While, therefore, the 
general plan of nutrition in the higher animals is the same as 
in the earthworm, yet the alimentary canal and the organs for 
distributing food by means of blood tubes are changed so that 
they can furnish to these larger, more active animals the greater 
supply of food required. 

A marked addition to the food-distributing organs of higher 
animals is an organ called the heart, which is composed of 
muscle, and has for its special work the forcing of blood along 
the blood tubes. 

Modifications of the alimentary canal.— One way in which 
the alimentary canal of higher animals is modified is by being 
distended into a sac — the stomach — into which food is received 
from the mouth, and detained until partly digested. 

Another modification is the arrangement of the intestine in 
loops. This arrangement allows a greater length of intestine 
to be tucked away in a small space; and the greater length of 
intestine gives increased power to digest food. 



ANIMAL NUTRITION 



50 



12- 




Another modification is the targe groups of cells, called 

glands, which make from the blood the Huids that are poured 
into the canal and aid digestion. One of these fluids is the 
saliva of the mouth. 
These are in addi- 
tion to the digestive 
fluids that are se- 
creted in the walls 
of the stomach and 
intestine. 

Birds.— As birds 
have no teeth they 
cannot break up 
grain in their 
mouths. The grain 
passes on at once to 
an enlargement of the canal, called the crop, where it is moist- 
ened with saliva. Farther along the canal there is an oval 
enlargement of the canal called the gizzard. Its two sides con- 
sist of thick muscular w^alls, lined with a tough, horny mem- 
brane. Between the w^alls of the gizzard the moistened grain 
is crushed and ground into fine particles. The gizzards of 
these birds always contain small pebbles, or other hard sub- 
stances, which were swallowed to aid in the crushing of the 
grain. On leaving the gizzard the crushed grain passes on into 
the intestine, where digestion is completed. 

Cud-chewing animals. — Still another arrangement of the 



ALIMENTARY CANAL OF BIRD 

1. Tongue. 2. Windpipe. 3. Esophagus. 4. Crop. 5, 
6. Bronchi. 7. Stomach containing gastric glands. 
8. Gizzard. 9. Intestine. 10. Liver. 11. Pancreas. 
12. Kidney 



60 



PHYSIOLOGY FOR YOUNG PEOPLE 




A COW'S STOMACH 



alimentary canal is seen in the stomach of cud-chewing animals, 

such as the cow, sheep, goat, deer, camel, and antelope, which 

feed upon grass and 
other vegetable 
food. The stomach 
of these animals is 
divided into differ- 
ent compartments, 
usually four in num- 
ber. A cow tears 
off the grass, chews 
it slightly, mixing it 
with saliva, and 

then rolls the moistened grass into a ball and swallows it. This 

ball of grass passes down the esophagus into the first, and 

largest, chamber of 

the stomach, and 

from there passes on 

into the second 

chamber. When the 

cow is ready to chew 

her cud, a ball of the 

food is forced up the 

esophagus into the 

mouth. It is then 

chewed and mixed with saliva until it becomes semi-fluid, when 

it is swallowed a second time. This time the openings into the 




SECTION OF A COWS STOMACH 



ANIMAL NUTRITION 



61 



first and second chambers are closed and the food passes into 
the third chamber, and thence into the fourth, where it is 
mixed with another digestive fluid. In time the food passes 
on into the intestine, where 
digestion is completed. 

Another interesting mod- 
ification of the alimentary 
canal is found in the camel. 
This animal is often unable 
to find water for days at a 
time. On the inner surface 
of the first and second cham- 
bers of its stomach is a large 
number of little pockets, or 
water cells, which can be 
closed up. In these water 
can be stored so as to be 
used later when needed. 
Because of this storage of 

water, a camel can travel across a desert for four or five days, 
or even longer, without drinking. Some persons believe that 
during journeys in the desert camels are sometimes killed in 
order that their drivers may relieve their own thirst with water 
from the stomach of the camel. But camel drivers say this is 
not true. 

Oxidation in animals. — Since food has to be oxidized in the 
cells of the body, in order to produce heat and the power to 




WATER POCKETS IX CAMELS STOMACH 



62 PHYSIOLOGY FOR YOUNG PEOPLE 

work, it is necessary that the cells should receive also a supply 
of oxygen. This oxygen is obtained directly from the air by 
animals that live on land, and from air contained in water by 
animals that live in water. Perhaps you do not know that 
water contains air, but you can easily prove it for yourself. 
If you will let a glass of water stand for some .time in a warm 
place, small bubbles of air from the water will accumulate on the 
inner side of the glass. When water in a vessel is heated over 
a fire, bubbles of air are driven off before the water commences 
to boil, and if a fish is placed in water that has been boiled and 
cooled, it will die from lack of air, for the air was driven out 
of the water by the heat. 

In the case of low^er animals that live in water, oxygen passes 
through the surface of the body and also through the lining of 
the digestive sac into spaces between the cells. The oxygen 
then passes along these spaces, and the cells take what is 
needed for the purpose of oxidation. 

The earthworm breathes through its skin. In its skin there 
is a vast number of minute blood tubes. Oxygen from the air 
passes through very small pores in the skin and through the 
thin walls of the minute blood tubes into the blood, which con- 
veys the oxygen to the cells of the body. If the earthworm is 
exposed to the heat of the sun, its moist skin soon becomes 
dry, and the worm dies because it can no longer breathe through 
its skin. Oxygen will pass through an animal membrane only 
when it is moist. 

In larger, more active animals, however, there is need of a 



ANIMAL NUTRITION 



63 




greater supply of oxygen, and in such animals there are special 
organs by means of whfch oxygen is obtained either from the 
air, or from air contained in water. An example of such special 
organs may be seen 
in the gills of com- 
mon fishes. The 
gills lie just behind 
the mouth. The 
fish takes water in- 
to its mouth, and 
then, by an act that 
resembles swallow- 
ing, causes this 
water to pass out 
over the gills. Only 

a thin membrane separates the blood in the blood tubes of the 
gills from the surrounding water. In this membrane are pores 
so fine that oxygen can pass through them into the blood, but 
the water cannot pass through to the blood, and the blood can- 
not pass through to the water. This oxygen is then conveyed 
in the blood to the cells of the fish's body and used to oxidize 
food. A fish cannot use oxygen from the air. When the little 
leaflets of their gills become dry, breathing becomes impos- 
sible; for a supply of oxygen from the air can pass through 
animal membranes only when these membranes are moist. 

Insects are very active, and require a large amount of oxygen 
in order to oxidize sufficient food to enable them to make their 



GILLS OF A FISH 



64 



PHYSIOLOGY FOR YOUNG PEOPLE 



rapid and frequent movements. Insects, accordingly, have an- 
other kind of breathing apparatus. Along their sides are small 
openings; air-tubes extend inward from these and branch off to 
all parts of the body. By means of these 
fine air-tubes, air is conveyed directly to 
the spaces between the cells in all the tis- 
sues, and the cells take from the air the 
oxygen that they need. 

In higher animals there are organs 
called lungs in which oxygen from the air 
enters the blood. Animals that breathe 
by lungs cannot take the oxygen that they 
need from air contained in water, and 
soon die if kept under water. Many lung- 
breathing animals, such as beavers, otters, 
seals, and walruses, spend much of their 
time in water, while whales spend all of 
their time in water. These animals can 
remain under water only a short time; 
they must come to the surface to breathe. 
A whale usually comes to the surface to take breath every ten or 
fifteen minutes. Seals are said to come to the surface about 
every seven minutes, and in winter, when wide areas of the sea 
are covered with ice, they keep holes open to which they come 
to take breath. 

Some animals, like the frog, can breathe both in air and in 
water. When on land a frog breathes through its lungs, but 




AIR-TUBES OF A 
BEETLE 

1. Air- tubes (shaded). 
2. Nerves 



ANIMAL NUTRITION 65 

when under water it breathes through its skin. Its skin is abun- 
dantly supplied with small blood tubes, and oxygen from the 
air contained in water passes through the thin wall of these 
blood tubes into the blood. 

Waste matters. — Whenever food is oxidized in an animal or 
a vegetable cell, waste matter is produced that consists chiefly 
of carbon dioxide, and water in the form of vapor. The cell 
must get rid of these, and they pass out of the body in the same 
way that the oxygen enters, but in the opposite direction. 

In both the plant and the animal cell, the wearing out of 
protoplasm produces waste matter. In the plant cell, the 
protoplasm can use this waste matter again in the act of repair- 
ing its loss; but in the animal cell, this waste matter must be 
got rid of. It passes out of the cell and is finally cast out of the 
body. In the highest class of animals, the mammals, this waste 
matter is called urea. It passes out of the cell into the blood, 
and is later taken from the blood by the kidneys. If this waste 
matter should remain in the body it would act as a poison and 
cause death. 

SUMMARY 

1. Even one-celled animals, such as the amoeba, take food into their 
bodies, digest it, and use it up. 

2. Such animals as the jelly-fish digest food in a stomach, and the 
digested food goes directly from the stomach to the cells of the body. 

3. The earthworm has an alimentary canal for digesting food, and a set 
of blood tubes for conveying it to the cells of the body. 

4. In higher animals, a heart forces blood along the blood tubes. 

5. In higher animals, there are modifications of the alimentary canal. 



66 PHYSIOLOGY FOR YOUNG PEOPLE 

6. Birds that eat grain have a gizzard to grind it. 

7. The stomach of cud-chewing animals is divided into compartments. 

8. A camel has in the wall of its stomach pockets in which to store a 
supply of water. 

9. Water contains air dissolved in it. 

10. Lower animals living in water get oxygen through the surface of the 
body and through the lining of the stomach. 

11. The earthworm gets oxygen from the air through the skin if it is 
moist, but cannot if it is dry. 

12. Fish get oxygen through the gills from air in water. 

13. Insects have air-tubes through which air goes directly to the cells 
of their bodies. 

14. Higher animals breathe by lungs. They lake oxygen from air, but 
cannot take it from air dissolved in water. 



CHAPTER VII 
DIGESTION 

What digestion is.— Before food 
can be used to nourish the body it 
must be changed so that it can pass 
into the blood tubes, become a part 
of the blood stream, flow to the tis- 
sues, and feed their cells. This 
changing of food is called digestion, 
and is carried on in the ali- 
mentary canal. 

The alimentary canal.— 
This canal is one long food 
tube and different parts of it 
have different names. The 
whole tube is about thirty feet long. 
Its upper opening is the mouth. 
Next comes the part known as the 
pharynx, which is about four and 
one-half inches long. Below the 
pharynx the canal is named the 
esophagus. This part of the canal 
is about nine inches long, and passes 

through the diaphragm into the abdo- 

67 




Large 
Intestine 



ALIMENTARY CANAL 



68 PHYSIOLOGY FOR YOUNG PEOPLE 

men. Here the tube expands into a sac called the stomach. 
Then it narrows again into the coiled part known as the small 
intestine, which is about twenty-five feet long. The tube then 
widens and ends in the large intestine, which is about five feet 
long. The work of digesting food begins in the mouth, and is 
continued in the stomach and in the intestine. 

DIGESTION IN THE MOUTH 

Mastication. — In the mouth, food is torn apart, moistened, 
and softened. The grinding and tearing are done by means of 
the teeth, assisted by the cheeks, the lower jaw, and 
the tongue. By means of powerful muscles the 
lower jaw can be moved freely back and forth, 
sidewise, and up and down. Into it is set a semi- 
circle of teeth that work with tearing and grind- 
a section ing movements against another semi-circle of teeth 
showiTg * n ^ e u PP er j aw - The upper jaw is immovable. 
enamel, Each tooth consists of a crown, a neck, and a 

CROWN, 

cavity, root or roots. 

The crown is the part above the gums, and is 
visible in the mouth. The neck is the narrowed part between 
the crown and the roots. The roots fit into holes in the jaw- 
bone. 

A tooth is hollow. Here is a picture of half a tooth that has 
been cut open. The central hollow portion contains the pulp. 
This pulp is composed largely of blood tubes and nerves which 
enter the teeth through openings in their roots. 




DIGESTION 



69 



r^i 




Three kinds of material make up the solid portion of a tooth. 
The main part is composed of a bony substance called dentine, 
which surrounds the pulp cavity. The crown is coated with a 
hard, white, shining material 
called enamel — the hard- 
est substance in the body. 
The root is crusted over 
with a cement that resem- 
bles bone in structure. 

The first tooth usually 
appears at the age of six or 
eight months, and is fol- 
lowed by others at irregular 
intervals, until the first, or 
temporary, set of twenty 
teeth is complete, at about the age of two and a half years. 

The second, or permanent, teeth begin to appear, as a rule, 
during the sixth year, and the w r hole set is generally complete 
by the twenty-fifth year. The permanent set consists of thirty- 
two teeth. The upper and lower jaws each contain four in- 
cisors, two canines, four bicuspids, and six molars. The in- 
cisors and canines have thin, cutting edges and are useful for 
biting. The bicuspids and molars have broad surfaces, which 
are used in grinding the food. 

Care of the teeth. — If a muscle, a bone, or a portion of the 
skin is injured, it at once begins to try to heal itself — and usu- 
ally succeeds. But, unlike other parts of the body, the teeth 



A SET OF UPPER TEETH 



70 PHYSIOLOGY FOR YOUNG PEOPLE 

have no power to repair any injury that may happen to them. 
It is important, therefore, to save them from injury as much as 
possible. To this end they should be kept scrupulously clean. 
Particles of food that are allowed to remain between the teeth 
decompose quickly, owing to the heat and moisture of the 
mouth. Decomposing food makes the breath unpleasant, and 
forms acids that injure the enamel and cause the teeth to decay. 
A soft wooden toothpick, or a piece of silk thread may be used 
to remove particles of food from between the teeth, but pins or 
metal picks should not be used, because the enamel is likely to 
be injured by them. It is not safe to crack nuts with the teeth, 
or to bite hard objects of any kind, because in this way a piece 
of the enamel may be broken off. Whenever the enamel is 
broken off, the tooth may decay and a cavity be formed. If 
the decay proceeds until a nerve is exposed, the tooth may 
become very painful. Every one should have his teeth exam- 
ined twice a year by a dentist, so that cavities may be 
promptly found and filled, and the gums may be treated, if they 
are receding. 

How saliva is made. — Saliva, the digestive fluid that mois- 
tens the mouth, is made in small organs called salivary glands. 
A gland consists of a group of cells surrounded by a network of 
fine blood tubes. The cells of a gland take up certain materials 
from the blood, and from these make a new material, which is 
called a secretion. Little tubes, called ducts, convey the saliva 
from the glands to the mouth. 

There are three pairs of salivary glands. One pair, the 



DIGESTION 



71 



parotids, lie just under each ear. Another pair, the submaxil- 
lary glands, lie in the front of the neck below the angle of the 
lower jaw. A third pair, the sublingual glands, lie under the 
tongue. 

When a person is not eating, these glands work slowly, and 




THE SALIVARY GLANDS, a, b, AND C 

just enough saliva is made to keep the mouth moist. But when 
food is taken into the mouth, they work rapidly, and saliva 
is poured out in abundance. The amount of saliva made 
in twenty-four hours is estimated to be about a pint and a 
half. 



72 



PHYSIOLOGY FOR YOUNG PEOPLE 



How saliva acts on food.— The chief purpose of saliva is to 
moisten and soften dry food. Moist food is easily masticated 
and swallowed. 

In addition to this, saliva contains a kind of ferment, called 

ptyalin, that acts on 
starch and changes it into 
a kind of sugar called 
maltose. Starch will not 
dissolve in a fluid, nor will 
it pass through the walls 
of the blood tubes. Sug- 
ar, however, will dissolve 
and will pass through the 
walls of the tubes into the 
blood. But saliva does 
not act on meat or other 
proteid food, or on fats. 
During an ordinary meal 
some of the starch in food 
escapes the action of the 
saliva and reaches the 
stomach as starch; some 
is partly changed, and some is completely digested and reaches 
the stomach as sugar. 

If we eat rapidly there is not time for the mixing of a suffi- 
cient amount of saliva with the food. We should, therefore, 
always eat slowly, and chew the food until it is in fine particles. 




THE PHARYNX 



DIGESTION 



73 



How food is swallowed. — When food is sufficiently moistened 
and masticated, it is pressed backward by the tongue, and passes 
into the part of the alimentary canal called the pharynx. 

The pharynx lies behind the mouth, and leads to the esoph- 
agus. After the food has been pressed backward by the 




THE PARTS OF THE MOUTH THE SAME PARTS IN SWAL- 

IN BREATHING LOWING 

n, the nasal cavity; r, roof of the mouth; p, soft palate; I, lid over opening into wind- 
pipe; w, windpipe; e, esophagus; t, tongue; t', tooth; /, food that is being swallowed 
(Landois and Stirling) 

tongue, the muscles in the wall of the pharynx contract and 
force the food on into the upper end of the esophagus. In the 
wall of the esophagus are muscles arranged, for the most part, 
in a circular manner. In the act of swallowing, muscles behind 
the food contract, narrow the esophagus, and thus keep pushing 
the food onward until it reaches the stomach. Drink is swal- 
lowed in exactly the same way as food. It does not run down 
the esophagus itself, but each portion that is swallowed is forced 



74 PHYSIOLOGY FOR YOUNG PEOPLE 

along by contraction of muscles behind it. This explains how 
horses and many other animals are able to drink when their 
heads are low, and how a juggler can drink while standing on 
his head. 

The pharynx connects also with the nose, and air on the way 
from the nose to the windpipe passes through the pharynx. As 
food is going back into the pharynx it must pass over the en- 
trance to the windpipe. This entrance is called the glottis, and 
is guarded by a lid called the epiglottis. When we are breathing, 
the epiglottis remains up, so that air may pass freely from the 
nose to the windpipe; but, when we swallow anything, the epi- 
glottis bends over and covers the glottis. If a drop of water, or 
a tiny morsel of food, enters the windpipe, a fit of coughing is 
sure to follow in order to expel it. 

DIGESTION IN THE STOMACH 

Location of the stomach.— As you will see from the picture 
on page 75, the stomach lies in th? upper part of the abdomen, 
on the left side, just under the heart. It has two openings. The 
upper one, by which food enters from the esophagus, is called 
the cardiac opening. The lower one, through which the partly 
digested food passes into the intestine, is called the pylorus, or 
gatekeeper. 

What the stomach is.— The stomach is a sac-like part of 
the alimentary canal. In its wall are layers of muscle. The 
inner surface of the stomach has a soft lining of mucous mem- 
brane, a kind of skin that lines the interior surface of the whole 



DIGESTION 



/•> 



of the alimentary canal and all other cavities that communicate 

directly with the air. At the lips, where it joins the outer skin, 




STOMACH IX ITS NATURAL POSITION 
s, stomach ; /, liver; g, gall bladder; p. pancreas ; i, intestine 

this membrane may be seen. Mucous membrane contains 
small glands that secrete a watery fluid, called mucus, which 
is poured out on the surface of the membrane to keep it moist. 



76 



PHYSIOLOGY FOR YOUNG PEOPLE 



The size of the stomach varies from time to time. When it 
contains no food its wall contracts and it becomes smaller. 
The entrance of food causes it to dilate again. 

The .muscles in the wall of the 
stomach are gathered into a 
thick, circular ring at the pylo- 
rus. When this ring of muscle 
contracts, the gateway is closed, 
so that no food can go through. 
When these muscles relax, the 
gateway opens and the contents 
of the stomach are allowed to 
pass into the intestine. 

Gastric glands. — The mu- 
cous membrane lining the stom- 
ach is composed almost wholly 
of small tubular glands, which 
secrete a juice called gastric juice. 
This is a sketch of a gland 
that secretes gastric juice. A gastric gland is surrounded by a 
network of tiny blood tubes, called capillaries. The cells in the 
lower part of the gland absorb material from the blood in the 
tubes, and from it make the juice which flows through the upper 
part of the gland into the stomach. When no food is in the 
stomach the cells rest, and when food comes in they work 
rapidly, and an abundant supply of gastric juice is made and 
poured on the food. 




GASTRIC GLAND 
(Magnified) 



DIGESTION 77 

Gastric juice looks like water. It contains a small amount 
of acid, which gives it a sour taste. It also contains substances 
called ferments. One of these, pepsin , can digest all forms of 
proteid food, while another, rennet, or rennin as it is sometimes 
called, assists in the digestion of milk. 

As soon as food of any kind enters the stomach, tiny drops 
of gastric juice appear at the mouths of the glands, trickle 
down the sides of the stomach in small streams, and mingle 
with the food. At the same time, movements of the stomach 
begin. Muscles in the wall of one end of it contract and cause 
the food to flow in the gastric juice toward the other end. Then 
the muscles in the wall at the other end contract and cause the 
food and the gastric juice to flow back again. These movements 
are called the peristaltic movements of the stomach. By them 
the gastric juice and the food are thoroughly mixed together. 
The digestion of food in the stomach is slow when it is too full. 
The peristaltic movements take place more readily when the 
stomach is about two-thirds full. 

How gastric juice acts on food.— Gastric juice digests all 
forms of proteid food, such as those found in lean meat, eggs, 
milk, and vegetable food. By its action, these foods gradually 
fall apart and become dissolved in the juice itself. Gastric 
juice does not dissolve fat or starch. When milk is taken into 
the stomach it is first curdled by the rennet of the gastric juice. 
Then the pepsin dissolves the curdled lumps and digests the 
proteid they contain. 

Babies often throw up part of a meal of milk in a curdled 



78 



PHYSIOLOGY FOR YOUNG PEOPLE 



condition. The throwing up is nature's way of getting rid of 
part when too much is taken, and does not always mean that 
the baby is ill, or that he is unable to digest his food. The 

curdling shows that digestion 
has already begun, for curd- 
ling is the first step in the 
digestion of milk. The curds 
are always larger and firmer 
when cow's milk is used. In 
feeding infants on cow's milk 
the curds will be softer and 
more finely divided if a table- 
spoonful of lime-water, or 
barley-water, is added t 
each feeding. 

As soon as a portion of the 
food in the stomach becomes 
dissolved the muscles at the 
cardiac end contract and the 
food is pushed toward the pylorus. The thick ring of muscle that 
closes the pylorus relaxes and allows the more liquid contents 
to escape into the intestine; but on the approach of lumps of 
undigested food the pyloric ring closes quickly. The peristaltic 
movements of the stomach then continue until another part of 
the food is dissolved, when it, in turn, is forced on into the 
intestine. 

The length of time during which food remains in the stomach 




END OF LARGE INTESTINE 

1. Caecum. 2. Ileum. 3. Colon. 4. Valve 
of Ileum. 5. Appendix 



DIGESTION 79 

varies much under different circumstances. On an average, 
the stomach is nearly, if not quite, empty in four or five hours 
after a meal. 

Until recently it was supposed that a man could not live 
without his stomach, but cases have been recorded in which the 
stomach was removed because of disease, and the patient con- 
tinued to live. 

DIGESTION IN THE INTESTINE 

What the intestine is. — The intestine is the part of the 
alimentary canal that extends downward from the stomach, 
forming the lowest part of the canal. The upper part of the 
intestine is small in diameter, and is called the small intestine. 
Its average length is about twenty-five feet. The lower part is 
larger in diameter, and is called the large intestine. Its length 
varies from four and a 
half to five feet. 

Different parts of the 
intestine have different 
names. The first ten or 
twelve inches from the 
stomach are called the 

SECTION OF SMALL INTESTINE 

duodenum. The first 

two-fifths of the rest of the small intestine are called the jejunum, 
and the remaining three-fifths are called the ileum, which opens 
into the large intestine. The name colon is given to the part of 
the large intestine that is above the valve of the ileum, and the 




80 PHYSIOLOGY FOR YOUNG PEOPLE 

name ccecwn is given to the short part below the valve. From 
the caecum there is a worm-like projection called the vermiform 
appendix. In the disease appendicitis there is an inflamma- 
tion of the appendix. 

The wall of the intestine consists largely of muscle. On the 
inside it has a soft lining of mucous membrane. A picture of 
the mucous membrane of a part of the small intestine is shown 
on page 79. The membrane is drawn up into folds, and this 
arrangement increases its secreting surface. The folds also 
retard the passage of food along the intestine, and allow more 
time for digestion. 

The process of digestion is completed in the intestine. When 
the food leaves the stomach it is a thick, soup-like fluid, called 
chyme. It contains undigested starch that has escaped the 
action of saliva, undigested proteid that has escaped the action 
of the gastric juice, portions of starch and proteid only partly 
digested, and also digested proteid, sugar, fat, water, and salts. 

Food is digested in the intestine by the action of the pan- 
creatic juice, which is made in the pancreas; the bile, which is 
made in the liver; and the intestinal juice, which is made by 
glands in the wall of the intestine. 

The pancreas.— The pancreas lies in the abdomen, behind 
the lower part of the stomach and the upper part of the intes- 
tine. It is a long gland, of a reddish cream color, resembling 
the salivary glands, and has often been called the abdominal 
salivary gland. The pancreas of the ox and other animals is 
known by the name of sweetbread, which we often use as food. 



DIGESTION 



81 



How pancreatic juice acts on food. — The pancreatic juice 
is the most important of all the digestive juices, for it contains 

■■■A 




THE LIVER AND PANCREAS 

Part of the stomach cut away to show pancreas 
I, liver ; g, gall bladder ; s, stomach ; i, intestine ; p, pancreas 

three ferments. One of these acts on starch, changing it to 
maltose, a kind of sugar. This action resembles the action on 
starch of ptyalin in the saliva, but is more rapid. Another fer- 



82 PHYSIOLOGY FOR YOUNG PEOPLE 

ment digests proteids. Its action resembles that of the pepsin 
in gastric juice. The third ferment acts upon the fats in the 
food, and digests them. The pancreatic juice enters the duo- 
denum through a duct, or tube, about four inches below the 
pylorus. 

The liver. — You have often seen ox liver or calf liver. The 
human liver, as you will see from the picture on page 81, resembles 
ox liver. It lies under the diaphragm, close to the lower ribs of 
the right side. As it is the largest gland in the body, and one 
of the most important, it has a number of duties to perform. 
Among these is the making of bile. The liver is made up of 
cells and blood tubes, held together by connective tissue. These 
cells take from the blood what is necessary to make bile. When 
digestion is going on, the bile comes directly from the liver to 
the intestine, through a little tube. The tube from the pan- 
creas and the one from the liver unite and the bile and pan- 
creatic juice enter the duodenum by the same tube. When 
digestion is not going on, the bile is stored up in a little pear- 
shaped bag, the gall bladder, which is tucked away under the 
liver. It is very necessary to health that the bile should escape 
from the liver to the intestine. When for any reason the bile 
cannot escape readily enough, it passes into the blood, and is 
carried to all parts of the body, causing a condition known as 
jaundice. 

How bile acts on food.— The bile by itself has little or no 
power to digest food. It aids the pancreatic juice, especially 
in digesting fats, lessens fermentation in the intestine, and 



DIGESTION 83 

stimulates the peristaltic movements of the wall of the intes- 
tine, which cause its contents to move along toward its lower 
end. 

How the intestinal juice acts on food.— The action of the 
intestinal juice on food is caused by a ferment that has the 
power to change cane-sugar and maltose into grape-sugar. It 
has also some power to change starch into grape-sugar. 

The muscles in the wall of the intestine, by their contractions, 
which are called peristaltic movements, force the food along 
and cause it to become thoroughly mixed with the pancreatic 
juice, the bile, and the intestinal juice. 

As a result of the changes produced by the action of the di- 
gestive fluids of the mouth, the storriach, and the intestine, the 
food which was swallowed as meat, bread, butter, and so on, 
becomes liquefied. The part of this liquid that is fit to nourish 
the body is now ready to be taken out of the intestine into the 
blood tubes, where it will become a part of the blood. 

A part of our food, however, is not fit to nourish the body. 
This part, consisting of indigestible and undigested matter, 
cannot be taken into the blood. It remains in the intestine and 
is forced along by the contraction of muscles in the intestinal 
wall, until it passes out of the body as useless material. It is 
important that the bowel, as the intestine is sometimes called, 
should get rid of this useless material every day. Regular habit 
in this matter is necessary in order to avoid constipation and 
other troublesome disorders. 



84 PHYSIOLOGY FOR YOUNG PEOPLE 

ABSORPTION OF FOOD 

You have now followed the process of digestion until it is 
completed in the intestine. There in the intestine is the ma- 
terial that will supply heat, repair waste, and produce the power 
to work. How are the muscles, the bones, the brain, and all 
the different parts of the body to get this material ? They can- 
not go to it. It must be brought to them. The first step is to 
get this food into the blood. 

A small amount of sugar and even some digested proteid 
food pass through the mucous membrane of the stomach into 
the blood tubes in the wall of the stomach, become part of the 
blood stream, and flow in the blood to the different parts of the 
body. But the main portion of food gets into the blood from 
the intestine. 

The villi. — When the surface of the mucous membrane that 
lines the small intestine is examined carefully, it is seen to have 
a velvety appearance. This is owing to the presence of a very 
large number of tongue-like bodies, called villi. There are 
about four millions of these villi in the small intestine, but none 
at all in the large intestine. The use of the villi is to absorb 
food from the intestine so that it may pass on into the blood. 

In the picture of a villus, which is highly magnified, you 
can see that it is composed of three main parts — a layer of cells 
on the surface; a network of very small blood tubes, called 
capillaries, underneath ; and a larger tube, called a lacteal, in the 
centre. The arteries that lie in the mucous membrane of the 



DIGESTION 



85 



intestine Send a branch up to the base of each villus, and this 

branch, passing upward into the villus, divides into many small 

branches, forming a capillary network just under the layer of 

cells. At the opposite side of the villus these capillaries unite 

to form a vein that passes down to join 

a larger vein in the mucous membrane 

of the intestine, below the base of the 

villus. The lacteal of the villus joins a 

tube below, called a lymph tube. Lymph 

tubes contain a colorless, watery fluid 

called lymph. It is derived from the 

blood, and, later, it passes back into the 

blood. 

The villi project inward from the en- 
tire inner surface of the small intestine, 
and their cells are bathed by any liquid 
contained in the i&testine. As the di- 
gested food, which is now in liquid 
form, moves along in the intestine, the 
cells of the surface of the villi absorb it, 
and from these cells it passes on into the interior of the villi. 
After the food has passed into the villi, practically all the sugar, 
digested proteids, salts, and water that it contains pass at once 
through the thin walls of the capillaries, and mix with the blood 
that is already there. This part of our food then flows on into 
the veins and is conveyed by them to the heart. 

The fat that has been absorbed into the villi passes into the 




86 PHYSIOLOGY FOR YOUNG PEOPLE 

lacteals and on to the lymph tubes in the wall of the intestine. 
When digestion is not going on, the lymph in the lacteals and 
lymph tubes of the intestine is a watery fluid. But when the 
fine particles of fat from the food pass into the lacteals and 
mingle with the lymph, they give it a milky appearance. This 
milky fluid is no longer called lymph, but is called chyle. The 
chyle flows along the lymph tubes of the intestine into a larger 
tube called the thoracic duct. The contents of the thoracic 
duct pass into a large vein near the left side of the neck, and 
there mingle with the blood. (See page 107.) 

The cells of the different parts of the body take from the 
blood the fats, proteids, sugar, salts, and water that they need, 
and use this material in different ways. The proteid part is 
used for repair of waste and for growth. The fats and carbohy- 
drates are burned up in the cells, producing heat and power. 
Sometimes proteid also is burned up in the cells. This process 
is called oxidation. It takes place in most of the tissues of the 
body, but especially in the cells of the muscles and the glands, 
because these are the most active cells in the body. 

As the sugar, salts, water, and digested proteids are going 
from the intestine to the heart they pass through the liver. 
During digestion more sugar is brought to the liver than is 
required for immediate use in the body. Part of this sugar is 
taken up by the liver cells, changed into a substance called gly- 
cogen, and stored in the cells until it is needed. When more 
sugar is needed by the cells of the body, the liver cells change 
the glycogen back into sugar and allow it to pass out into the 



DIGESTION 87 

blood, and it also is oxidized in the cells of the tissues, giving 
out heat and power. 

Effects of alcohol on the stomach.— Alcohol, like pepper, 
mustard, and other condiments, has a direct irritating effect on 
the mucous membrane that lines the stomach. It causes the 
small blood tubes in the lining to dilate and contain more blood 
than usual, and gives rise to a feeling of warmth in this organ. 
If only a small amount of alcohol is taken it is quickly absorbed 
into the blood tubes and carried away in the blood. The blood 
tubes remain dilated for a short time and then return to their 
usual size. 

If alcoholic liquor is taken frequently, even in moderate quan- 
tity, the mucous lining of the stomach is constantly irritated, 
the blood tubes are kept dilated and congested, and the glands 
in the wall of the stomach pour out an increased amount of 
mucus. The mucus in a healthy stomach is a thin, watery 
fluid, and is secreted in small quantities in order to moisten the 
mucous lining. Under the irritating influence of alcohol an 
unhealthy, sticky mucus is secreted that coats the stomach wall. 
This unhealthy mucus greatly interferes with digestion, and 
frequently causes nausea and vomiting, especially in the morn- 
ing. In later stages, patches of the mucous membrane may 
become so injured that they waste away and leave sores, or 
ulcers, in the wall of the stomach. 

The large amount of fluid that is often taken by beer drinkers 
stretches the wall of the stomach and greatly increases the size 
of this organ. This stretching weakens the muscles in the wall 



88 PHYSIOLOGY FOR YOUNG PEOPLE 

of the stomach so that food is not forced on into the intestine so 
promptly as it should be. This is a frequent cause of painful 
indigestion. 

Effects of alcohol on the liver.— A large part of the alcohol 
that is swallowed is absorbed into the veins in the wall of the 
stomach, and is carried at once by the blood to the liver. Since 
it is the first organ to receive the alcohol after it enters the blood, 
the liver is greatly affected. On account of the irritating action 
of alcohol the blood tubes of the liver soon become dilated, 
and the whole organ becomes congested just as the blood tubes 
of the skin become congested when mustard is applied to it. 

On those cells of the liver which secrete bile and store up 
glycogen, alcohol acts as a poison. At first these cells swell, 
and the liver becomes enlarged. If the action of the alcohol is 
continued for some time, the protoplasm of these liver cells 
changes more or less completely to fat, and the power of the 
cells to perform their work is greatly lessened. 

The liver cells are held together by connective tissue. This 
tissue, as we have learned, is made up of cells with a large amount 
of intercellular material which is made by the cells. The con- 
nective tissue cells also of the liver are injured by the irritant 
action of alcohol. When a constant irritation is kept up, even 
by small amounts of alcohol passing through the liver, the con- 
nective tissue cells often increase in number. The new cells 
may develop into permanent connective tissue, taking the place 
of liver cells that have been destroyed, and also pushing aside 
and destroying other liver cells. 



DIGESTION 89 

One function of the liver is to oxidize, and so render harm- 
less, minute harmful substances in the blood. Some of these 
are due to the using up of proteid food in the process of nutri- 
tion ; others may arise from various forms of disease. As blood 
containing such substances is passing through the liver, they 
are oxidized and thus prevented from injuring the tissues later. 
It has recently been discovered that even very moderate amounts 
of alcoholic liquor interfere to a marked degree with this im- 
portant function of the liver. 

SUMMARY 

1. Food must be digested so that it can pass from the alimentary canal 
into blood tubes. 

2. Digestion takes place in the mouth, the stomach, and the intestine. 

3. In the mouth, food is torn apart by the teeth, and moistened and 
partly digested by the saliva. 

4. The teeth should be kept clean, and cavities should be filled promptly. 

5. Saliva contains a ferment, ptyalin, which can change starch to sugar. 

6. Food should be well chewed and well mixed with saliva. 

7. The epiglottis closes over the glottis when we swallow and prevents 
food from entering the windpipe. 

8. Small glands in the mucous lining of the stomach secrete gastric juice. 

9. This juice contains two ferments: pepsin, which digests proteid food, 
and rennet, which curdles milk. 

10. Three digestive juices enter the intestine: pancreatic juice, bile, 
and intestinal juice. 

11. Pancreatic juice can digest proteid, starch, and fat. 

12. The bile aids pancreatic juice in digesting fat. 

13. The intestinal juice acts upon cane-sugar and maltose. 

14. The mucous lining of the small intestine has a large number of little 
projections called villi. These absorb from the intestine the part of our 
food that can be used in the cells of the body. 



90 PHYSIOLOGY FOR YOUNG PEOPLE 

15. The proteid food, sugar, salts, and water go into the blood at once 
and then pass through the liver. 

16. The fat goes into lymph tubes, on into the thoracic duct, and then 
into the blood. 

17. Alcohol irritates the mucous lining of the stomach. 

18. The continued irritation of the mucous lining causes an unhealthy 
secretion of mucus, and may cause sores or ulcers in the wall of the stomach. 

19. Alcohol injures the blood tubes and cells of the liver. 

20. Alcohol interferes with oxidation in the liver, and harmful substances 
that should have been made harmless remain in the blood. 



CHAPTER VIII 



THE CIRCULATION OF THE BLOOD 

Uses of the blood. — The flow of blood throughout the body 
is called the circulation of the blood. As the blood flows 
through all parts it carries food and oxygen to the cells of the 
tissues. It distributes to all 
parts of the body the heat 
that is produced by the oxi- 
dation of food in the cells. 
If the skin, for example, 
were to receive no blood, it 
would soon become cold. 
While the blood is supply- 
ing food and oxygen to the 
cells of the tissues, it is also 
collecting waste matter from 
them and carrying it away 
to organs that expel it from 
the body. The heart, the 
arteries, the capillaries, and the veins are the organs that carry 
on the circulation of the blood. 

What the heart is. — The heart is a hollow organ composed 
of muscle tissue. , It is about the size of a man's closed fist, 
and has the shape of an inverted pear. As you will see from 

91 




THE HEART, RIBS AND STERNUM 



92 



PHYSIOLOGY FOR YOUNG PEOPLE 



the picture, the heart lies in the chest behind the ribs, but ex- 
tends more to the left than to the right of the middle line. It is 

enclosed in a sac, called the 
"pericardium, which is com- 
posed of serous membrane. 
This is a thin membrane 
that lines cavities of the body 
that do not communicate 
with the air.- Serous mem- 
brane secretes a watery fluid 
that keeps its surface moist 
and slippery. The small 
end, or apex, of the heart 
points downward and tow- 
ard the left; it lies within 
the thorax close to the chest 
wall. 

A partition, called the sep- 
tum, divides the heart into a 
right and a left side. This 
partition completely sepa- 
rates one side from the other, so that no blood can get through. 
Each side of the heart consists of two chambers, an upper 
and a lower one. The upper chambers are called auricles and 
the lower chambers are called ventricles. 

In this picture the outer wall of the right side of the heart has 
been removed so that you can see into the interior. Two large 




3— 



INTERIOR OF RIGHT SIDE OF HEART 

1. Aorta. 2. Pulmonary artery. 3. Inferior 
vena cava. 4. Superior vena cava. 

From "'Gray's Anatomy" 



THE CIRCULATION OF THE BLOQD 93 

veins open into the right auricle, and all the blood from every 
part of the body flows into the auricle through these veins. 
The wires marked B in the picture show how these veins open 
into the auricle. There is an opening through which the blood 
passes from the right auricle into the right ventricle. You can 
find this opening in the picture by a wire marked A that has 
been passed through it. A valve, like a little door, guards the 
opening. It is called the tricuspid valve, and consists of three 
segments, or flaps, the edges of which come together when it 
closes. As the ventricle becomes full of blood the valve closes 
and prevents the blood from flowing back into the auricle when 
the ventricle closes. Cords fastened to the flaps and to the 
sides of the ventricle prevent the flaps from being pushed out 
into the auricle as the blood in the ventricle presses against the 
flaps. 

There is an opening through which the blood passes from 
the right ventricle into an artery called the pulmonary artery, 
which divides into two branches, one going to each lung. This 
artery can be seen at the right upper corner of the picture. 
Valves guard the opening into the pulmonary artery, and pre- 
vent blood from flowing back from the artery into the ventricle. 

We have on page 94 a picture of the interior of the left side of 
the heart. Four veins, called pulmonary veins, open into the left 
auricle. In the picture these openings are shown by the figures 
3, 4, 5, 6. There is an opening from the left auricle into the 
left ventricle. Its position is shown in the picture by a wire 
marked B. The valve that guards the opening, and prevents 



94 



PHYSIOLOGY FOR YOUNG PEOPLE 



blood from flowing back into the auricle, is called the mitral 
valve, because it looks like a mitre which a bishop wears on his 
head. There is an opening from the left ventricle into a very 

large artery, called the 
aorta. The position of 
this opening is shown in 
the picture by a wire 
marked A. Valves guard 
the opening into the aorta 
and prevent blood from 
flowing back into the 
ventricle. 

This description, to- 
gether with the pictures, 
will give you some idea 
of the heart, and what its 
important parts are. Let 
us now find out some- 
thing about the arteries, 
the veins, and the capil- 
laries. We shall then be 
ready to follow the course of the blood as it circulates through 
the body by means of all these organs. 

The arteries. — The arteries are strong tubes, which are, as 
a rule, below the surface of the body, and are thus protected 
from injury. The wall of an artery contains tough elastic 
tissue and muscle tissue. In the wall of a small artery there is 




INTERIOR OF LEFT SIDE OF HEART 

1. Aorta. 2. Pulmonary artery. 3, 4, 5, 6, 
Pulmonary veins 

From ' ' Gray' s Anatomy ' ' 



THE CIRCULATION OF THE BLOOD 95 

a smaller proportion of elastic tissue and a larger proportion of 
muscle than in the wall of a large artery. The muscle fibres 
are wrapped around the artery at right angles to its length, very 

a a 



: r /f " 






* 



>J 



HEART AND AORTA 
a, a, a, Branches of Aorta 



much as you would wrap a bandage around your finger. 
Muscles have the power to contract and become shorter. 
When these muscles contract they lessen the size of the artery 
just as squeezing it with your hand would lessen its size. 



96 PHYSIOLOGY FOR YOUNG PEOPLE 

The aorta, which starts from the left ventricle, is the main 
artery of the body. It commences at the upper part of the 
left ventricle, ascends a little way, then bends over to the left 
behind the heart, so as to form an arch like a horseshoe. Then 
it passes through the thorax and abdomen, in front of the spine. 

Beginning at a very short distance from the heart, branches 
are given off from the aorta throughout its entire length. Some 
of them pass upward to the neck and head; others pass outward 
to the arms and hands. Lower down, branches also pass off 
to the stomach, liver, kidneys, and other organs. One large 
branch goes to each leg. 

All these branches of the aorta are called arteries, and as 
they pass out through the body they divide and subdivide many 
times. Each time they divide they become smaller and their 
walls become thinner. 

The capillaries. — After the arteries divide many times, they 
become so small and so numerous that they form a fine net- 
work of hairlike tubes. The wall of each tube consists of a 
single layer of flattened cells, like little plates, joined at their 
edges. These tiny, thin tubes are no longer called arteries, 
but their name is changed to capillaries. With few exceptions, 
the cells of every tissue are surrounded by a network of capil- 
laries so small that you cannot see them without a microscope, 
and having a wall that is much thinner than tissue paper. 

The veins. — The tiny capillaries soon unite with one another 
to form larger tubes, and these unite again and again to form 
still larger ones, while at the same time their walls become 



TIIK CIRCULATION OF THE BLOOD 



97 



thicker. These larger tubes are called veins. They are at first 
only slightly larger than the capillaries; but as they continue 
to unite they form, each time, larger veins. The wall of a 

9v 




'^8 



SECTION OF HEART, SHOWING THE FOUR CAVITIES 
1. Superior vena cava. 2. Inferior vena cava. 3. Right auricle. 4. Right 
ventricle. 5. Pulmonary artery. 6, 6. Pulmonary veins. 7. Left auricle. 
8. Left ventricle. 9. Aorta 

vein is thicker than the wall of a capillary, but it is thinner than 
the wall of an artery. It contains a smaller amount of elastic 
tissue and muscle. Most veins have valves that prevent the blood 
from flowing backward. A valve consists of a fold of the lining 
membrane of the vein. 



98 



PHYSIOLOGY FOR YOUNG PEOPLE 



You will see from what has preceded that there is only one 
set of blood tubes, but the different parts have different names. 
All the tubes that go from the heart out to all parts of the body 
are called arteries. All the tubes that go back to the heart 



3mal£ 




ARTERY, CAPILLARIES, AND VEIN 
(Magnified) 

are called veins. The little tubes that connect the arteries and 
veins are called capillaries. 

Course of the blood.— The work of the heart is to receive 
the blood that is conveyed to it from all parts of the body 
through the veins, and immediately to force the blood out again 
to all parts of the body through the arteries. The walls of the 
heart are composed of muscles which contract, or shorten, and 
relax, or lengthen. When these muscles relax, the heart 




THE CIRCULATION OF THE BLOOD 99 

chambers open and blood flows in from the veins. When "these 
muscles contract, the chambers close and the blood is forced 
out into the arteries. The two auricles contract together, and 
immediately afterward the two ventricles contract together. 
Each time that the heart contracts, we say 
that it beats. By placing the hand on the 
chest, a little to the left side, you can feel 
every beat of the heart. 

Turn to the picture of the right side of the 
heart on page 92. Find the superior vena 
cava. These are Latin words for the upper 
hollow vein. It is through this vein that 
blood flows to the right auricle from the 
upper part of the body. Find the inferior VALVE OF VEIN 
vena cava. These are Latin words for the lower hollow 
vein. It is through this vein that blood flows to the right auricle 
from the lower part of the body. Find, by means of the wires, 
the opening from the vena cava superior and the vena cava in- 
ferior into the right auricle. When the right auricle opens, 
dark venous blood pours into it from the vena cava superior 
and from the vena cava inferior. Some of this blood runs on 
at once through the opening into the right ventricle. As soon 
as the auricle is filled, the blood in it is pressed into the 
ventricle. 

The pulmonary circulation. — Before the blood is sent back 
to nourish the body it must get a supply of oxygen, and this 
can be obtained only from the air in the lungs. The flow of 



100 PHYSIOLOGY FOR YOUNG PEOPLE 

the blood from the right side of the heart out to the lungs for 
oxygen and back again to the left side of the heart is called the 
pulmonary circulation. The artery through which the blood 
goes to the lungs is called the pulmonary artery. Find in the 
picture on page 92 the opening into this artery. It is through 
this opening that the blood is next forced by the contraction of 
the right ventricle. The pulmonary artery divides into two 
branches a little above the heart. One branch passes under the 
arch of the aorta and goes to the right lung. The other branch 
bends to the left and goes to the left lung. The dividing of the 
pulmonary artery continues until all the air sacs of the lungs are 
surrounded by a perfect network of tiny tubes — the lung capil- 
laries. Through the thin walls of these capillaries the blood 
gets from the air in the lungs the oxygen that it needs. These 
tiny capillaries connect w r ith small veins which lead back 
toward the heart. The small veins unite again and again until 
they form the pulmonary veins by which the blood enters the 
left side of the heart. 

The systemic circulation.— The blood is now ready to carry 
both food and oxygen to all parts of the body. The flow of the 
blood from the left side of the heart out to all parts of the body 
and back again to the right side of the heart is called the sys- 
temic circulation. Turn to the picture of the left side of the 
heart on page 94. Find the openings from the pulmonary 
veins into the left auricle. As the bright arterial blood flows 
through these openings into the left auricle, some of it passes 
at once through the opening into the ventricle. The auricle, 



THE CIRCULATION OF THE BLOOD 101 

however, is soon filled, and it then closes and presses its con- 
tents into the ventricle. Find the opening from the left ven- 
tricle into the aorta in the picture on page 94. It is through 
this opening that the blood is forced into the aorta by the con- 
traction of the left ventricle. From the aorta the blood flows 
into the large aortic branches, then into the smaller arteries, 
and so on until it reaches the capillaries that surround the cells 
in the tissues of the body. 

The blood as a whole does not leave the blood tubes. But 
while it is passing along the capillaries the oxygen and certain 
portions of the blood, which we may describe as the food, pass 
through the thin unbroken capillary wall, and fill the tiny spaces 
between the cells of the tissues. After it has passed through the 
capillary w T all this fluid is called lymph. At the same time 
certain w^aste matter leaves the cells of the tissues and passes 
through the thin capillary wall into the blood. In the capil- 
laries the blood loses its bright arterial color and becomes a 
dark bluish red. This is because it has given up its oxygen to 
the tissues. Laden w r ith waste matter, it makes its way from 
the capillaries into small veins, thence to the larger veins, thence 
into the vena cava superior and the vena cava inferior, and back 
into the right side of the heart. The time taken by a drop of 
blood in making the entire circuit is probably about half a 
minute. 

The portal circulation.— The blood from the blood tubes 
of the stomach and the intestine flows into a single vein called 
the portal vein. The portal vein enters the liver, and there 



102 PHYSIOLOGY FOR YOUNG PEOPLE 

divides and subdivides into capillaries. These capillaries unite 
to form three veins which, on passing out of the liver, join the 
vena cava inferior. This flow of the blood through the portal 
vein to the liver and on through capillaries and veins into the 
vena cava inferior is called the portal circulation . 

How the circulation may be affected.— The circulation of 
the blood may be hindered in many ways. Large veins lie just 
under the skin and near the surface. Tight clothing does not 
allow the blood to flow freely and easily through these veins. 
Tight boots make cold feet, because they interfere with the free 
flow of the blood. Tight garters, also, are a frequent cause of 
cold feet. The heart needs plenty of room in order to do its 
work well. Tight waists and other tight clothing press in the 
soft walls of the chest and interfere with the free action of the 
heart. 

The pulse. — The pulse is caused by the beating of the heart. 
Each time the left ventricle contracts it forces a quantity of 
blood into the aorta. This blood strikes against the column 
of blood already in the aorta and starts a wave that travels 
along the blood in the arteries and causes the throb of the artery 
wall. This throb is called the pulse. It may be felt in any 
artery that is near the surface. A convenient place to feel it 
is at the wrist near the base of the thumb. It is because of this 
wave-like movement of blood along the arteries that it flows 
from a wounded artery in spurts; whereas, if a vein is wounded, 
blood flows from it in a steady stream. 

The heart beats about seventy-two times a minute, but the 



THE CIRCULATION OF THE BLOOD 103 

number of beats varies very much even in health. Active exer- 
cise, and such feelings as fear, surprise, or joy cause the heart 
to beat faster or slower than usual. 

We count the pulse when we wish to know how fast the heart 
is beating. When a physician places his finger on an artery he 
is able to tell much about the strength of the heart, as well as 
the rapidity of its beat. 

The health of the heart. — It must be plain to every one that 
it is most important to have a sound, healthy heart. If the 
heart is weak or the valves are imperfect, the blood cannot be 
discharged into the arteries with sufficient force to cause free 
circulation to all parts of the body. 

Rheumatism is a frequent cause of heart disease, even in 
children and young people. In order to prevent this disease, 
as far as lies in our power, we should be careful not to live in 
damp houses. We should also avoid sitting on damp ground, 
and if our clothing becomes wet, we should change it without 
delay. 

Excessive, violent muscular exercise is apt to dilate the heart 
and injure it. Persons that are feeble and delicate are more 
likely to be injured in this way than those that are strong and 
robust. 

Bicycle riding in moderation is excellent exercise as a means 
of strengthening the heart, though when carried to excess it is a 
frequent cause of injury to it. 

The blood. — Blood, as it flows from a cut or wound, is a red 
fluid. It looks to the naked eye as if it were composed of one 



104 



PHYSIOLOGY FOR YOUNG PEOPLE 




RED AND WHITE CORPUSCLES 
(Magnified) 



kind of material only; but, when it is examined with a micro* 

scope, it is found to consist of two materials : a watery fluid, the 

plasma; and little cells, the corpuscles, which float in the plasma. 

The plasma. — The plasma is a transparent, almost colorless 

fluid. iVbout ninety per cent, 
of it consists of water. The 
plasma contains proteids, sugar, 
salts, and fats derived from the 
food, and some waste matter 
from the tissues. 

The corpuscles.— The corpus- 
cles are extremely small bodies. 
This picture shows how they 
appear when seen through a 
microscope of high magnifying power. They are of two kinds, 
red and white. The white corpuscles are slightly larger than 
the red ones. 

Three thousand five hundred red corpuscles placed side 
by side would make a row an inch long, and two thousand 
five hundred white corpuscles placed side by side would make 
a row of equal length. This will give you some idea of how 
the red and the white corpuscles compare in size. 

The color of the blood is due entirely to the red corpuscles 
that it contains. Their use is to carry oxygen from the lungs to 
the tissues. These corpuscles float along in the blood stream 
of the arteries. When they reach the capillaries, oxygen es- 
capes from the corpuscles and passes through the thin capillary 



THE CIRCULATION OF THE BLOOD 105 

wall into the cells of the tissues. The red corpuscles then float 
hack in the veins to the heart and go out to the lungs for more 
oxygen. 

If a coin were hollowed out slightly on each side, its shape 
would be verv much like the shape of a red corpuscle. 

There are immense numbers of these corpuscles in the blood. 
A drop of the blood of an average healthy man contains about 
five million red corpuscles. 

The white corpuscles are less numerous than the red. There 
are about five hundred red corpuscles for each white one. The 
white corpuscles have a peculiar power of movement by which 
they are able to alter their shape. At times they are spherical; 
at other times they thrust out an arm-like projection in one 
direction, or several projections in different directions, and 
their shape becomes extremely irregular. 

These corpuscles are able to pass through the w^alls of the 
capillaries and wander about in the neighboring tissues. When 
any part of the body has been wounded, they collect around the 
w r ound and prevent bacteria and other injurious matter from 
entering the blood. The white corpuscles often succeed in 
destroying and removing bacteria in a wound, but sometimes 
they are beaten in the battle and are themselves destroyed. 
Then they form a part of the pus that flows from the w r ound. 
They also serve to protect the body from the invasion of germs 
that produce disease, and they assist in the clotting of blood. 

How the supply of blood to organs is regulated.— The 
blood stream carries food and oxygen to all parts of the body. 



106 PHYSIOLOGY FOR YOUNG PEOPLE 

Oxygen is carried by the red blood corpuscles; food is dissolved 
in the plasma and is carried by it. 

The amount of blood required by any organ is not the same 
at all times. When an organ is actively at work, it requires a 
greater supply of blood because it needs more nourishment; but 
when an organ is at rest, or is less active, it needs less blood. 

When food enters the mouth, the salivary glands become 
more active. They pour out an increased amount of saliva; 
and, at the same time, the small arteries in these glands dilate and 
allow an increased amount of blood to come to these organs. 

When the stomach must get ready to digest food, it requires 
more blood to help do its work. The muscles in the small 
arteries in the wall of the stomach relax; and, as the arteries 
dilate, more blood comes to the stomach. 

As we go to sleep the brain becomes less active than when 
we are awake. During sleep the blood tubes in other parts 
of the body dilate and contain more blood than usual, so that 
less blood comes to the brain when it is at rest. 

The muscles in the walls of the small arteries are connected 
by nerves with the brain and spinal cord. Messages, without 
our knowing it, pass along these nerves when required, causing 
the muscles to contract and lessen the size of the arteries. So 
long as the messages continue to come to the muscles they 
remain contracted, and the arteries contain less blood. If the 
messages are few, or cease entirely to come, the arteries become 
dilated and contain more blood. In this way the supply of 
blood to different parts of the body is continually regulated by 



THE CIRCULATION OF THE BLOOD 107 

nerves. More blood comes to any given part when it is active, 
and less blood when the part is not active. 

Clotting of blood. — Blood is perfectly fluid when it first 
escapes from a cut or wound. It soon, however, becomes 
sticky and in five or ten minutes changes to a jelly-like mass. 
The mass, in a short time, contracts and becomes much smaller. 
It is then called a clot. While the mass is contracting an 
almost colorless fluid, the serum, is squeezed out, and the clot 
floats in this serum. 

Clotting of blood is caused by a change in a part of the plasma 
by which fibrin is formed. When a clot is examined w T ith a 
microscope it is seen to consist of corpuscles enclosed in a 
tangled mass of fine hair-like fibrils of fibrin. While the fibrils 
are being formed they entangle the corpuscles, as in a spider's 
web, and then form the clot. A clot forms because of changes 
that take place in the blood itself, and not because it is exposed 
to the air. Fibrin may be obtained by whipping fresh blood 
with a bunch of little twigs. The fibrin will adhere to the twigs 
in the form of tiny threads, or fibrils. 

The use of the clot is to stop bleeding. It acts as a plug and 
prevents the escape of blood from a torn or cut blood tube; 
when the tube stops bleeding one should be very careful not to 
disturb the clot. 

The lymph tubes and the thoracic duct.— In the tissues of 
the body there is a system of tubes that are quite distinct from 
the blood tubes. They contain a colorless watery fluid called 
lymph, and are called lymph or lymphatic tubes. 



108 



PHYSIOLOGY FOR YOUNG PEOPLE 






7 - 




WW 




THORACIC DUCT AND LYMPH TUBES 

1. Lymph tubes of head and neck, left side. 2. Veins of left shoulder. 3. Lymph 
tubes of left arm. 4. Thoracic duct. 5. Lymph tubes of intestine, called 
lacteals. 6. Lymph tubes of left leg. 7. Vena cava superior 



THE CIRCULATION OF THE BLOOD 109 

The following pictures show some of the lymph tubes of the 
hand and of the arm and trunk. You can see how the smaller 
tubes unite to form larger ones. The current of lymph in the 
tubes is always toward the heart. 

The lymph contained in the lymph tubes is derived from the 
blood. While the blood is flowing through the capillaries in 




LYMPH TUBES OF HAND 



the various parts of the body, some of the plasma of the blood 
oozes out through the thin capillary walls into the tiny spaces 
between the cells of the surrounding tissues. After. this watery 
part has oozed through the capillary walls it is called lymph. 
Some of the lymph, after bathing the cells of the tissues, and 
giving up nourishment to them, may pass back into the capil- 
laries, but a large part of it enters the lymph tubes, which are 
specially provided for it. 

These tubes start from the little spaces between the cells, and 
unite again and again to form larger tubes. The picture on page 
108 shows how the small lymph tubes of the lower part of the body, 



110 



PHYSIOLOGY FOR YOUNG PEOPLE 



the intestine, and the left side of the upper part of the body pour 
their contents into a larger tube called the thoracic duct. This 
duct ascends in front of the spinal column and pours its con- 
tents, consisting of mingled chyle from the intestine and lymph, 

into a vein of the left shoulder, 
at a point where this vein joins 
a vein from the neck. Here 
the contents of the thoracic 
duct join the blood stream as 
it is on its way to the vena 
cava superior, a short, large 
vein formed by the junction 
of two veins, and to the right 
auricle of the heart, Another 
set of lymph tubes collect 
lymph from the right side of 
the upper part of the body, 
and pour it into a vein of the 
right shoulder, at a point 
where this vein joins a vein from the neck. Here the lymph 
joins the blood stream as it is on its way to the vena cava 
superior and the right auricle of the heart. 

Effects of alcohol on the circulation. — A moderate amount 
of alcohol causes the heart to beat faster for a short time, and 
the pulse becomes fuller. The fuller pulse may give a false im- 
pression and lead to the belief that alcohol stimulates the heart 
and makes it beat with greater force. The change in the pulse 




LYMPH TUBES OF ARMS AND TRUNK 



THE CIRCULATION OF THE BLOOD 111 

is due to the fact that alcohol causes the small arteries through- 
out the body to dilate. The large bounding pulse, which gives 
a deceptive appearance of vigor and force in the circulation is 
due to the change in size of the dilated arteries. 

There is no evidence that alcohol acts as a direct stimulant 
to the heart, or that it causes the heart to beat with greater 
force. In small quantities its action on the heart is slight, but 
in large amounts it has a powerful effect in depressing the heart 
and weakening the force of its beat. 

The long continued use of alcoholic liquors, especially of beer, 
often leads to an increase of fat in the muscle fibres of the heart, 
and also between them. As the heart thus becomes weakened 
it becomes larger and less able to perform its work well. The 
so-called " beer-drinker J s heart" is larger than it should be, and 
has an unusual amount of fat on its surface as well as in its 
muscle fibres and between them. It is a heart that is liable to 
fail when an unusual strain, as in disease, is put upon it. 

The continued drinking of alcoholic liquors often causes per- 
manent changes in the walls of the blood tubes. The walls 
become thickened and less elastic. They may also be further 
weakened by fat in their muscles. This diseased condition of 
the blood tubes interferes very seriously with the circulation of 
blood and nourishment of the body. 

Soon after the Olympian games in the spring of 1906 the 
following cable despatch appeared -in the New York Sun: 
"Berlin, May 19. — German writers, in commenting on the 
failure of German athletes to carry off signal honors in the 



112 PHYSIOLOGY FOR YOUNG PEOPLE 

Olympian games at Athens, assert emphatically that the chief 
cause of the low standard of their physical achievements is 
the beer-drinking habit, which is greatly sapping the national 
vigor. 

"Several writers agree that this habit prevents the Germans 
from acquiring that tautness of muscle which distinguishes the 
American and English athletes, and not only causes superfluous 
fat but seriously affects the heart, which is the sport organ par 
excellence." 

On this point it is well to remember the words of the late 
General von Moltke, Commander of the German army: "Beer 
is a far more dangerous enemy to Germany than all the armies 
of France." 

The following statements from American athletes who were 
winners in the Olympian games at London in 1908, show the 
practice of many athletes in this country in regard to the 
drinking of alcoholic liquors: 

Bayonne, N. J., December 30, 1908. 

Dear Sir: — In reply to your letter of the 18th inst. requesting 
a statement as to the effect of alcoholic liquors and tobacco, I 
can say that my experience of eighteen years has shown me that 
alcoholic liquors and tobacco should not be used during periods 
of training. If this abstinence keeps the body in the best con- 
dition for feats of strength, it certainly shows that, if we want 
to live a long healthy life, we should leave alcohol and tobacco 
alone. Yours truly, 

Ray C. Ewry, 

(Champion, Standing High Jump, and Standing Broad Jump.) 



THE CIRCULATION OF THE BLQOD 113 

Cleveland, Ohio, January 27, 1909. 
Dear Sir: — As an athlete throughout my school-day career and 
since, I have always found it wise to abstain from the use of 
narcotics and alcoholics. 

Faithfully yours, 

Harry Franklin Porter, 
(Champion, Running High Jump.) 

New York, January 24, 1909. 
Dear Sir: — From a competitor's stand-point, athletes in training 
for different events greatly retard progress in conditioning them- 
selves by the use of alcoholic beverages or tobacco in any form, 
as their use affects one's staying pow T ers — particularly for gruelling 
contests. Yours truly, 

Harry Hillman, 
(400 Meters Hurdle.) 

SUMMARY 

1. The blood carries food and oxygen to the cells. 

2. The blood distributes heat to all parts of the body. 

3. The blood collects waste matter from the cells and carries it away. 

4. The work of the heart is to receive blood from all parts of the body 
and to force it out again to all parts. 

5. From the right side of the heart blood goes to the lungs, and then to 
the left side of the heart. This is called the pulmonary circulation. 

6. From the left side of the heart blood goes out to all parts of the body, 
and then back to the right side of the heart. This is called the systemic 
circulation. 

7. The flow of blood from the stomach and intestine through the liver 
is called the portal circulation. 

8. The circulation of blood should not be hindered by tight clothing. 

9. The pulse is the throb in the wall of an artery because the heart has 
forced more blood into it. 



114 PHYSIOLOGY FOR YOUNG PEOPLE 

10. The heart may be injured by rheumatism and by excessive violent 
exercise. 

11. The blood consists of the plasma and the corpuscles. 

12. The plasma conveys food in solution; the red corpuscles convey 
oxygen. 

13. The white corpuscles destroy bacteria and assist in the clotting of 
blood. 

14. When blood escapes from a blood tube it clots. The use of the 
clot is to stop bleeding. 

15. Plasma is called lymph after it passes through the walls of the capil- 
laries to carry food to the cells. 

16. Much of the lymph is returned to the blood by means of the lymph 
tubes. The largest of these is the thoracic duct. 

17. In moderate amounts, alcohol does not strengthen the heart. In 
large amounts, it weakens the heart. 

18. The continued drinking of alcoholic liquor, especially beer and 
wine, may cause an increase of fat in and also between the fibres of the 
heart. 

19. The continued drinking of alcoholic liquor may injure the walls of 
the blood tubes* 



CHAPTER IX 
IS ALCOHOL A FOOD? 

We have learned that when alcohol enters the stomach it 
passes into the small veins in the wall of the stomach and min- 
gles with the blood. It is then conveyed in the blood to the 
cells of tissues in different parts of the body just as food is 
conveyed to the cells. But when it reaches the cells, its action 
differs in important ways from the action of ordinary foods. 

The purposes of food are to build up and repair the tissues, 
and to serve as fuel. 

Only those foods which contain nitrogen, viz., proteid foods, 
can build up and repair the tissues. Alcohol does not contain 
nitrogen, and therefore cannot replace the worn-out substance 
of cells or build up new tissue in the body. Alcohol, then, is 
not a food in the sense that meat, eggs, gluten, and other pro- 
teids are food. 

Food is also the fuel of the body, and it is burned, or oxidized, 

in the cells of the tissues by uniting with oxygen just as truly as 

coal is burned in a furnace. When food is oxidized in the cells 

of the tissues, heat and power to work are produced. Sugar, 

starch, and fats are examples of foods that are useful as fuel. 

Such foods may be oxidized in a very short time after they 

reach the cells of the tissues, or they may be stored up for 

future use. 

115 



116 PHYSIOLOGY FOR YOUNG PEOPLE 

Experiments show that when a small amount of alcohol is 
taken into the body, nearly all of it is oxidized in the cells of the 
tissues. It is, however, always oxidized in a short time after it 
reaches the tissues, and is never stored up for future use. In 
this respect alcohol differs from starch, sugar, and other fuel 
foods. 

When a small amount of alcohol is taken it is oxidized in 
the cells of the tissues, and heat and power to work are pro- 
duced. Consequently, alcohol in small amounts acts in one 
way like a fuel food. But the mere fact that a substance is 
oxidized in the cells of the tissues does not show whether it is 
useful or harmful to the body. 

If alcohol is useful as a fuel food it ought to protect the body 
against cold. It should also add strength to the muscles and 
enable those who take it to do an increased amount of work. 
But the experience of officers in the army, of athletes, and of 
those who employ men in factories, on railroads, and in other 
laborious occupations, shows that men can do more and better 
work when they do not take alcoholic liquor than they can 
when they drink such liquor even in moderate amounts. The 
experience of explorers and lumbermen in the far north shows 
also that the drinking of alcoholic liquor is useless to protect 
the body against cold. It has been found that in those occupa- 
tions requiring close attention, keen senses, clear judgment, 
and steady nerves, the use of alcoholic liquor of any kind is 
always injurious. 

The chief reason why alcohol does not strengthen the mus- 



IS ALCOHOL A FOOD? 117 

cles and enable those who drink it to do an increased amount 
of work is because of its action as a drug. This is the most 
important difference between alcohol and substances that are 
usually called foods. The chief effect of food is to nourish and 
strengthen the body; the most important effect of alcohol is its 
action as a drug on the brain and nerves. 

Men, as a rule, do not take alcoholic liquor as food, but for 
the peculiar effect it produces on the brain. 

Suitable quantities of ordinary food are harmless to the 
tissues, and are absolutely necessary to maintain the body in a 
state of health. Alcohol is not necessary to a healthy body 
under any conditions or in any amount. 

Alcohol, then, is not a food in the ordinary sense in which 
we use that term, but it belongs to a class of dangerous drugs 
called narcotics. Its action resembles the action of such drugs 
as ether and chloroform. 

Poisonous action of alcohol.— The action of alcohol as a 
narcotic poison is plainly seen in the condition of intoxication 
that follows the drinking of large amounts of alcoholic liquor. 
The thickened speech,- staggering gait, drowsiness, and loss of 
consciousness in this condition are caused by the alcohol. In 
such cases it acts on the brain as a poison. 

Its poisonous action is plainly shown also by the changes 
that occur in the cells of the brain and other organs when the 
free indulgence in alcoholic liquor is continued for some time. 
Such changes lead, sooner or later, to disease in the organs 
affected. These diseases due to the drinking of alcohol some- 



118 PHYSIOLOGY FOR YOUNG PEOPLE 

times occur in persons who never drink alcoholic liquor in 
quantities sufficient to cause intoxication. 

The continued use of alcoholic liquors in moderate quantities 
does not affect all persons in the same way, or to the same 
extent. Some persons are more readily injured by it than 
others. In the case of some persons, the moderate use of 
alcoholic liquor as an occasional beverage with meals does not 
apparently shorten life or cause sufficient changes in any organ 
to produce disease that can be recognized. In the case of others, 
such moderate use produces gradual and permanent changes 
in internal organs, such as the heart, liver, and kidneys. These 
changes, as a rule, come on slowly and are not easily recog- 
nized at first, but gradually they tend to weaken the organs and 
injure the general health. 

The appetite for alcohol.— The chief danger in drinking 
an occasional glass of wine, beer, or other alcoholic liquor is 
not on account of any immediate harm that it may produce in 
the organs of the body. The great danger is in the tendency 
gradually to increase the amount as the body becomes accus- 
tomed to its use. Most people are apt to overestimate their 
power to resist this growing appetite for alcoholic liquor. The 
habit of drinking often fastens itself upon a man before he 
realizes that the habit is formed; and, when he finds it out, the 
habit has often become so strong that it does not seem possible 
to give it up. It is because the appetite for alcohol grows on 
one that many who begin as occasional or moderate drinkers, 
and intend to remain such, become, in time, hopeless drunk- 



IS ALCOHOL A FOOD? 11!) 

ards. Any kind of alcoholic liquor may cause this unnatural 
and uncontrollable appetite for alcohol. 

While it is true that some persons continue for years to 
drink small amounts of alcoholic liquor without apparent in- 
jury, it is also true that no one can be sure in advance that, if 
he commences as a moderate drinker, the habit will not grow 
upon him until he becomes a confirmed drunkard. The only 
safe course, therefore, is not to drink alcoholic liquor at all. 

A recent American medical work on poisons contains this 
statement regarding alcohol: "From almost every stand-point 
alcohol must be regarded as the most important poison with 
which medical men and jurists have to deal; no other poison 
causes so many deaths or leads to or intensifies so many dis- 
eases, both physical and mental, as does alcohol in the various 
forms in which it is taken/' — Text-book of Legal Medicine and 
Toxicology, Peterson and Haines, Vol. II, page 537. 

The following quotations are from a pamphlet on alcohol 
that is given to every young soldier and sailor on joining the 
German army or navy: 

" Alcoholic drinks do not quench the thirst so well as water, tea, 
coffee, and lemonade, and they contain no nutriment, or at least 
very little. Thus a glass of heavy beer, for which five cents are 
paid, has no more nutriment than a piece of cheese that costs a 
quarter of a cent. To give beer the name of liquid bread is, there- 
fore, not at all justifiable. " 

"We may say that almost all brawls and cases of disorderly con- 
duct are to be traced back to intoxication. And in most cases — 



120 PHYSIOLOGY FOR YOUNG PEOPLE 

which must be noted here very clearly — it is the beer that does so 
much harm. Beer is, therefore, by no means the harmless drink 
that so many consider it to be." 

"The military authorities adopt many measures in order to 
abate intemperance. Among these, there is an order that, on 
marches, field flasks shall be filled with non-alcoholic drinks; and 
there is strict supervision in regard to this rule." 

Before the days of modern machinery, each man began and 
completed a piece of work himself. If he was not in condition 
for turning out his best work, it was only his work that was 
spoiled or delayed. In these days, however, a number of men 
are employed on the same piece of work, each at his machine 
doing a small part of it. In order that work may be completed 
without delay, and may be done in the best manner possible, 
each man must be always in condition to turn out his best work. 
It is not surprising, therefore, that many large employers dis- 
courage and even prohibit the drinking of alcoholic liquors by 
employees. The letters that follow illustrate the stand that 
many employers take in this matter. 

Boston, Mass., January 25, 1909. 
Dear Sir: — Yours of January 22d has been duly received, and 
in reply to the same I will say, that for more than half a century it 
has been the policy of our house not only to discourage the use of 
alcohol by our employees, but it has been also absolutely prohibited 
during working hours. Our work necessitates specially trained 
mechanics of the highest class. These men remain with us usually 
for very many years, sons following father not infrequently in em- 
ployment in our factories. We do not presume to be the censor 



IS ALCOHOL A FOOD? 121 

of any man's conscience, or what he shall eat or drink, but we do 
not knowingly engage any man who indulges in the use of alcohol, 
because he would fail to remain with us for any length of time. 
Very truly yours, 

Mason & Hamlin Co., 
A. W. Wright, Vice-Pres. and Gen. Mgr. 

Boston, Mass., January 25, 1909. 

Dear Sir: — In reply to your letter of the 22d inst., we would say that 

we discourage, so far as we possibly can, the use of alcoholic liquors 

by all our employees. We are especially strict against the use of 

alcoholic liquors by employees having positions of responsibility. 

Yours truly, 

The Boston Bridge Works, Inc. 

Manchester, N. H., February 19, 1909. 
Dear Sir: — Replying to your letter of recent date, I beg to ad- 
vise that we do not allow the employees of any of the lighting or 
railway companies that we own to use alcoholic liquors while on 
dutv. Very truly yours, 

J. Brodie Smith, 

Vice-Pres. and Gen. Mgr. 
Manchester Traction, Light and Power Co. 

Pittsburg, Pa., January 11, 1909. 

Dear Sir: — Replying to your letter of the 4th inst., I beg to ad- 
vise that the only rule which this company has in effect with refer- 
ence to the use of alcohol, is as follows : 

"Employ steady, reliable, sober men only, in the capacity of 
mine foreman, fire boss, master mechanic, hoisting engineer, boiler 
and fan tenders, and stable boss; the use of intoxicating liquors 
by any employee while on duty is absolutely forbidden, and no 



122 PHYSIOLOGY FOR YOUNG PEOPLE 

employee will be allowed on the plant or permitted to enter the 
mine visibly under the influence of liquor." 
Yours very truly, 

H. C. Frick Coke Company, 
D. H. Coble, Secretary. 

SUMMARY 

1. Alcohol cannot replace worn-out matter in the cells or build up new 
tissue. 

2. Carbohydrate food may be oxidized in a short time in the cells, or it 
may be stored up in them for future use. 

3. Taken in small amounts, alcohol is oxidized in the cells; but it is 
oxidized in a short time. It is not stored up. 

4. The fact that a small amount of alcohol is oxidized in the cells , yield- 
ing heat and power to work, does not prove that it is a useful food. 

5. Alcohol does not add strength to the muscles. 

6. Alcohol does not protect the body against cold in severe climates. 

7. Alcohol is usually taken because of its effect as a drug on the brain 
and nerves. 

8. Alcohol should be classed as a narcotic poison. 

9. Its action as a poison is clearly seen in intoxication. 

10. It often produces in the cells of the brain and other organs serious 
changes that in time cause disease. 

11. The greatest danger in the moderate drinking of alcohol is that it 
may lead to an uncontrollable appetite for alcohol. 



CHAPTER X 
BREATHING 

Air. — Air is a mixture of gases. It is composed of a large 
amount of oxygen and nitrogen and a small amount of carbon 
dioxide and other gases. For animals the necessary gas in 
pure air is oxygen. They must have oxygen in order to live. 
Man can live a month without food; a few days without water; 
but only a few minutes without oxygen. We breathe on an 
average about eighteen times a minute. Oxygen enters the 
body with every breath. 

Some of the oxygen that we breathe in with the air enters the 
blood and is carried to the cells of the tissues, where it is used 
to oxidize the food. The oxygen, however, does not all pass 
into the blood, for the supply in pure air is so great, that, under 
ordinary circumstances, we require only about one-fifth of the 
amount that we take in. The remaining four-fifths are carried 
out again. 

The windpipe and the air tubes.— Air enters through the 

nostrils or mouth, then passes down through the windpipe, or 

trachea, into the lungs. The trachea divides at its lower end 

into a branch for each lung. On page 124 there is a picture of 

the trachea and its branches, together with an outline of each 

lung. The trachea begins at the larynx, or Adam's apple. 

123 



124 



PHYSIOLOGY FOR YOUNG PEOPLE 



The trachea varies from four to four and a half inches in 
length and is about three-quarters of an inch in diameter. 
Each of its branches, as you see in the picture, divides and sub- 




TRACHEA AND ITS BRANCHES 



divides many times, forming the bronchial tubes. The bron- 
chial tubes continue to divide and give off branches which 
become smaller and smaller until they end in tiny air sacs, com- 
posed of thin elastic tissue. Several air sacs are often grouped 
around the end of one small bronchial tube. 

Spasmodic croup. — This is an ailment that is common 
among little children. The child goes to bed well, and about 
midnight awakens with difficult breathing and a crowing cough. 



BREATHING 



L25 



difficulty in breathing. 




SECTION OF GROUP OF 
AIR SACS AT END 
OF SMALL BRONCHIAL 
TUBE 



The condition often appears very serious and causes great alarm, 
owing to the suddenness of the attack and the distress from 

These attacks are usually caused by a 
spasm, or cramp, in the muscles of the 
larynx, and are seldom serious. A large 
handkerchief wrung out of hot water and 
applied to the neck in front is usually 
sufficient to relieve the spasm in a short 
time. 

Membranous croup.— In the disease 
called diphtheria a thin, grayish-white membrane usually forms 
on the tonsils and other parts of the throat. Sometimes a 
similar membrane forms in the larynx, and gives rise to a very 
serious condition known as laryngeal diphtheria, or mem- 
branous croup. The disease begins with slight hoarseness and 
a croupy cough, which gradually becomes more severe. The 
membrane increases in thickness and soon fills the interior of 
the larynx, so that during respiration air 
passes in and out with great difficulty. 
Unless relief is obtained, suffocation quick- 
ly follows. The larynx can be kept open 
by means of a small tube which is put 
into it through the mouth. 

Asthma. — Asthma is a disease in which 
there are paroxysms or spells of difficult 
breathing. The attacks often come on in the night after a few 
hours of sleep. There is then a painful sense of want of breath, a 




GROUP OF AIR SACS AT 
END OF SMALL BRON- 
CHIAL TUBE, SHOW- 
ING CAPILLARIES IN 
WALLS OF SACS 



126 PHYSIOLOGY FOR YOUNG PEOPLE 

feeling of great oppression in the chest, and a desire to sit upright 
in order to get relief. The attack may pass off in a short time 
or may continue on and off for a few days. During the par- 
oxysms remove all tight clothing and 
allow an abundance of fresh air. 

Pneumonia. — Pneumonia is a dis- 
ease in which there is a local inflam- 
mation in the lung. It is one of the 
most common of all acute diseases, and 
occurs equally in cold and in hot coun- 
tries. People who live in cities and 
those who are exposed to hardship and 
cold are the most liable to have it. 

A simple kind of lung. — The lungs 
of animals are not all alike. In some 
the structure is more simple than in 
others. It will help us to understand 

THE LUNGS OF A NEWT . 

what our lungs are like if we first learn 
the structure of more simple lungs, such as are found in the 
newt, a little animal that somewhat resembles a lizard. 

A newt's lungs consist of two oval sacs and a very short wind- 
pipe. They resemble in some ways small toy balloons. The 
wall of a toy balloon is elastic. It swells out when the balloon is 
inflated and collapses when the air goes out of it. The wall 
also of the sac that forms a newt's lung is elastic. When the 
newt breathes in, its lungs swell out and become larger. When 
it breathes out, its lungs shrink and become smaller again, 




BREATH I XG 12? 

but the little sacs are never quite empty. They always contain 
some air. Tiny capillaries are fitted into the wall of each air 
sac, and form connecting links between the arteries and the 
veins in the sacs. 

What our lungs are like. — We have two lungs, one in the 
right side of the chest and one in the left. Thev are soft and 
spongy in texture and light pink in color. The left lung has 
two lobes, or divisions, and the right lung has three. The lungs 
rest on the broad, tough muscle called the diaphragm, which 
arches up into a sort of dome, and supports them. 

Each lung is covered with a smooth, delicate serous mem- 
brane called the pleura. The chest also is lined with it. Serous 
membrane, you remember, secretes a watery fluid that keeps 
its surface moist and slippery, so that though the pleura that 
covers the lung rubs against the pleura that lines the chest, 
there is no friction. You may have heard of a disease 
called pleurisy. It is the name given to an inflammation of a 
pleura. 

In our lungs there are more than eight hundred millions of 
tiny air sacs, and each one resembles the small sac that makes 
up one of the lungs of a newt. These air sacs are arranged 
around the ends of the bronchial tubes, so that the air which is 
breathed in passes along the bronchial tubes into the air sacs 
at their ends. Each sac is composed of thin elastic tissue 
with capillaries embedded in its wall (see cut on page 125). 
These capillaries are the connecting links between the arteries 
and the veins in the lungs. 



128 



PHYSIOLOGY FOR YOUNG PEOPLE 



Here is a picture of the lungs and heart. A portion of the 
right lung has been removed so that you can see the arteries, 
veins, and bronchial tubes within it. 




LUNGS AND HEART. PART OF LUNG CUT AWAY FROM LEFT SIDE TO 
SHOW BLOOD TUBES AND AIR TUBES 

Movements in breathing.— The act of breathing consists 
of two movements. We breathe in and we breathe out. When 
we breathe in, we are said to inhale, or inspire; when we breathe 
out, we are said to exhale, or expire. 

In breathing, the chest acts like a pair of bellows. When the 



BREATHING 129 

handles of a pair of bellows are drawn apart the sides are sepa- 
rated so that the cavity between them is enlarged, and air im- 
mediately passes in to fill the space. 

When you take a deep breath you simply enlarge the cavity, 
or holding capacity, of the chest, and the lungs expand to fill the 
increased space around them. When the lungs expand, each 
air sac becomes larger, and air passes in to fill the increased 
space. 

The expansion of the chest is due to the action of certain 
muscles. If you place your hands on your chest while breathing 
deeply, you can feel the wall of the chest moving. The muscles 
in the wall of the chest contract, so as to raise the ribs and 
breast-bone and cause them to move outward. At the same 
time the diaphragm, which forms the floor on which the lungs 
rest, contracts. This lowers the floor and more space is left for 
the lungs. In this way the capacity of the chest is increased 
in all directions. 

During expiration the muscles relax, and the diaphragm, the 
ribs, and the breast-bone return to their former positions. As 
the chest thus becomes smaller, its wall presses on the lungs 
and expels a portion of the air they contain. 

In quiet, ordinary breathing, about one-sixth or one-seventh 
of the air in the lungs is expelled at each expiration. 

Mouth breathing. — Air should always enter the lungs by 
way of the nostrils, because the nasal passages are so constructed 
that they delay the air within them long enough to strain dust 
from it, warm it, and moisten it, if it is too dry. A person that 



130 



PHYSIOLOGY FOR YOUNG PEOPLE 




makes a habit of breathing through the mouth is more likely to 
have lung diseases than one that breathes through the nose. 
Sometimes nose breathing is made difficult by little grape-like 
clusters in the back part of the nasal passages. They are called 
adenoid growths, and should be removed by a doctor; for, be- 
sides interfering with breathing, they 
may cause defective hearing. 

Breathing exercises.— Breathing 
exercises strengthen the muscles of 
the chest and increase the capacity 
of the lungs. They are especially 
desirable for those who have nar- 
row, contracted chests, and also for 
those who, because of delicate health, 
cannot safely take part in active, vig- 
orous games. 

The voice. — All sound is pro- 
duced by vibration, or rapid move- 
ment to and fro, of the air. In the 
case of the voice this vibration is produced by means of the vocal 
cords. The vocal cords are contained in the larynx, a box-like 
structure placed at the upper end of the windpipe. The walls 
of the larynx are composed of cartilage. 

This picture shows the front part of the outside of the larynx. 
The broad upper part, in which a deep notch is seen in front, 
is the thyroid cartilage. It forms a complete ring around the 
upper part of the windpipe. The thyroid cartilage rests on the 







THE LARYNX 

1. Thyroid cartilage. 2. Cricoid 
cartilage 



BREATHING 



131 




3 xg 



THE VOCAL CORDS IN QUIET BREATHING 



cricoid cartilage, and the projecting part of the thyroid just 
below the notch is sometimes called "Adam's apple." 

With the mouth wide open and the tongue drawn well for- 
ward, it is possible to see an 
image of the vocal cords in 
a small mirror held at the 
back of the throat. This 
picture represents a view of 
the vocal cords obtained in 
this way, and shows the in- 
side of the larynx. 1 repre- 
sents the root of the tongue just above the larynx, and 2 the 
epiglottis, which folds over and covers the opening into the 
larynx when we swallow. The two bands, 3 3, represent the 
vocal cords. The opening between them is called the glottis. 

During quiet breathing 
the vocal cords lie apart and 
the glottis is wide. While 
we are speaking or singing, 
the vocal cords come close 
together and the glottis is 
narrow, as is show T n in the 
picture. 

When the vocal cords are 
brought together they are made tense by the contraction of 
muscles in the larynx. Then, as a blast of expired air passes 
through the narrow glottis, it causes the tense vocal cords to 




THE VOCAL CORDS IN SPEAKING OR SINGING 



132 PHYSIOLOGY FOR YOUNG PEOPLE 

vibrate. The vibrations of the cords make vibrations in the 
air, which reach the ear and produce the sensations of sound. 

Exchange between blood and air in the lungs.— We have 
called the capillaries embedded in the walls of the air sacs the 
connecting links between the arteries and the veins in the lungs. 
To these tiny capillaries, branches of the pulmonary artery 
convey dark red venous blood from the right side of the heart 
to receive oxygen from the air in the air sacs; and from these 
capillaries branches of the pulmonary veins convey bright red 
blood, containing a fresh supply of oxygen, to the left side of 
the heart. Do not, however, get the idea that the blood and 
the air mix in the air sacs. They are always separated by the 
thin walls of the capillaries and the air sacs. But the oxygen 
passes through these walls into the blood. The moment the 
oxygen reaches the dark red corpuscles of the venous blood it 
changes them to a bright red. 

The purpose of breathing is not only to get a fresh supply of 
oxygen into the blood through the lungs, but also to allow car- 
bon dioxide to escape from the blood through the lungs. While 
the blood is flowing along the lung capillaries and taking in a 
new supply of oxygen, some of the carbon dioxide in the blood 
goes through the walls of the capillaries and air sacs, mingles 
with the air in the lungs, and is breathed out. 

Thus, you see, there is an exchange between the air and the 
blood in the lungs. Oxygen goes from the air to the blood, and 
carbon dioxide goes from the blood to the air. 

The air we breathe out is said to contain, also, a small amount 



BREATHING 133 

of poisonous animal matter. Except on a very hot day, expired 
air is wanner than inspired air, and contains more moisture. 
You can see this moisture in the form of watery vapor if you 
will breathe on a cold mirror. 

It is often said that the blood is purified in the lungs; but the 
lungs remove only a part of one of the impurities that the blood 
contains, viz., carbon dioxide. Other organs, the skin and the 
kidneys, remove a part of other impurities contained in the 
blood. The blood always contains some impurities; but, when 
the body is in a state of health, these impurities are kept from 
accumulating in the blood in sufficient amount to do harm. 

How blood is changed in the tissues of the body.— The 
bright arterial blood, you remember, is sent out from the left 
side of the heart, through the aorta and its branches — the ar- 
teries — on to the capillaries of the tissues throughout the body. 

\Yhile the blood is flowing along the capillaries of the tissues, 
oxygen leaves the red blood corpuscles and goes through the 
capillary walls to the cells of the tissues. \Yhen the red blood 
corpuscles lose oxygen they turn dark in color. While the oxy- 
gen is passing out to the cells of the tissues, carbon dioxide and 
other waste matter leave the cells and pass through the capil- 
lary walls into the blood. 

If the oxygen given off to the tissues is not all needed at once, 
it is stored up in the muscles and other tissues for future use. 

What we mean by bad air. — ^Yhen there is not enough 
oxygen in the body for its various organs they are unable to do 
their work properly, and the health is injured. 



134 PHYSIOLOGY FOR YOUNG PEOPLE 

The mind cannot be clear and bright, nor can the muscles 
be strong and active, if we breathe air that contains too little 
oxygen and too much carbon dioxide. 

Coal gas, from a stove or furnace, and the gas used for light- 
ing are both poisonous. Air containing them is injurious to 
health. Damp cellars and old wells often contain poisonous gas. 

A bad smell is nature's warning that our health may be in 
danger from something near us. Yet bad air does not always 
have a bad smell. Sewer gas and other poisonous gas may be 
entirely without odor. 

How good air is made bad.— Every time you breathe you 
take oxygen from the air and add carbon dioxide to it. If you 
shut yourself up in a small room by closing the windows and the 
door, you will soon make the air bad by breathing. In crowded 
rooms there is too little oxygen and too much carbon dioxide 
unless there is proper ventilation. 

Lights and fires in a room consume oxygen and give out car- 
bon dioxide. Decaying animal or vegetable matter in or near a 
dwelling is sure to pollute the air. Drain pipes, when defective, 
may allow poisonous gas to escape into dwelling houses. 

Coal stoves are sometimes sources of danger. If the dampers 
leading to the chimney are closed too soon after fresh fuel is 
added to the fire, a large amount of very poisonous gas may 
escape into the room. 

Pools of stagnant water should not be allowed near dwellings. 
If such pools are used to receive refuse they are sure to con- 
taminate the air. 



BREATHING L35 

Harmful effects of breathing bad air. — The harmful effects 
of breathing had air are proved in a striking manner by the 
story of the Black Hole of Calcutta. One hundred forty- 
six English prisoners were confined for eight hours in a small 
room, eighteen feet square, with only two narrow windows to 
admit fresh air. Out of this number ninety-six died during the 
first six hours, and there was a total of one hundred twenty- 
three dead at the end of the eight hours. Only twenty-three of 
the entire one hundred forty-six managed, by keeping near 
the open windows, to secure enough fresh air to preserve life. 
Those at a short distance from the windows were obliged to 
breathe the same air over and over again until it contained so 
little oxygen and so much carbon dioxide that it # could not 
sustain life. This story, of course, gives an account of an un-> 
usual event, but it serves to show the deadly effects of air that 
is deprived of oxygen and loaded with carbon dioxide. 

Air rendered slightly impure by breathing is not dangerous to 
life, but it is injurious to health. A stay of only one or two 
hours in a tightly closed room, with no means of allowing fresh 
air to come in or foul air to get out, produces drowsiness, dull- 
ness, and headache. In a badly ventilated school-room, the 
pupils soon become dull and appear stupid, because the mind 
cannot be clear and active without fresh air. 

In a room in which the air can be changed frequently by 
ventilation, each pupil does not need so many cubic feet of fresh 
air space as in a room in which the air cannot be frequently 
changed. The ventilation and air space of a class-room should 



136 PHYSIOLOGY FOR YOUNG PEOPLE 

furnish at least three thousand cubic feet of fresh air every hour 
to each pupil. If a room is well ventilated, one who comes in 
from outdoors finds the air fresh and sweet. If he finds the air 
close and oppressive at ordinary temperatures, the room is not 
well ventilated. 

Those that spend most of their time in badly ventilated rooms, 
into which the sun seldom or never shines, are pale and have a 
sickly appearance. In such persons the blood and tissues are 
starved for want of oxygen and poisoned by an excess of carbon 
dioxide, and the power to resist diseases of the lungs is greatly 
lessened. 

Ways of ventilating. — In order to keep the air in a room 
fresh, it is necessary to provide some means by which fresh air 
may be brought in and foul air may be allowed to escape. 

This is an easy matter in summer, for then windows and doors 
are open a large part of the time. But it is quite different 
in winter when all openings are tightly closed to keep cold 
air out; yet fresh air is just as necessary in winter as it is in 
summer. 

Every properly constructed house or public building is so 
arranged that, in the winter, fresh air can be brought in, warmed, 
and then distributed to every part of the building. 

In houses where no special means are provided for ventila- 
tion the supply of fresh air must come in through the windows 
and doors — chiefly through the windows. Care must be taken 
to avoid a draft, and especially a draft of cold air. But you can 
ventilate a room in several ways without making a draft. One 



BREATHING 137 

way is to raise the lower half of the window and place 4 under it a 
frame, like the frame of a fly screen, that has flannel instead of 
wire fastened to it. 

Another way is to raise the lower sash a few inches and fill the 
space under it with a board. Air will then pass in between the 
sashes, and will take an upward direction., Thus a direct cur- 
rent of air upon those in the room will be avoided. Any con- 
trivance for ventilation will answer that will admit a sufficient 
amount of air without producing a draft. 

The need of fresh air during the night is often overlooked. 
Sleeping apartments should be thoroughly ventilated during 
the day, and no one should sleep in a room in which there is not 
a window sufficiently open to admit plenty of fresh air. 

Every one should spend at least a small part of each day in 
the open air. Even on cold or stormy days, if your health is 
good, wrap up well and spend some time out of doors. To 
every healthy person a brisk walk on a frosty morning is a 
tonic. It raises the spirits, increases the circulation of the 
blood, and produces a feeling of comfort and strength through- 
out the system. 

Cleanliness. — Besides being properly ventilated, the houses 
in w T hich people live should be clean. Dust that is allowed to 
collect on floors and walls and furniture is breathed into the 
lungs, and injures the health. School-rooms, especially, should 
be clean; and, in order that they may be kept clean, they should 
have hardwood floors that can easily be scrubbed, or floor cover- 
ings that will not catch and hold the dust. Any loose-meshed 



138 PHYSIOLOGY FOR YOUNG PEOPLE 

floor covering, such as cocoa matting, is a collector of dust 
and disease germs. 

Suffocation. — Owing to accidental causes of various kinds, 
breathing may, at times, become difficult, or may entirely cease. 
Very prompt action is sometimes required to prevent death from 
suffocation. 

Smoke and fumes. — Whenever it becomes necessary to pass 
through sulphur fumes or smoke, a large wet handkerchief, a 
wet towel, or other wet cloth should be held over the mouth and 
nose, so as to prevent the fumes or smoke from passing into the 
lungs. 

Coal gas. — A common cause of suffocation is breathing coal 
gas from a choked or defective coal stove, from the fumes of 
burning charcoal, or from a gas burner. In all such cases 
prompt removal into the fresh air is necessary. 

Drowning. — In case of drowning, if the person taken from 
the water is still breathing, he should be carried, if possible, to 
the nearest house and put into a hot bath; or cloths wrung out 
of hot water may be applied to the chest and abdomen, and the 
body be briskly rubbed. Heat tends to increase the breathing 
and to stimulate the circulation. In all cases of suffocation, 
great care must be taken to remove at once all obstructions 
from the mouth and throat, so that fresh air can reach the lungs. 

Artificial respiration. — The object of artificial respiration 
is to imitate as nearly as possible natural breathing. This 
method should be promptly applied in suffocation where 
breathing has ceased, or has become very feeble. Full direc- 



BREATHING 139 

tions for doing this are given under "What to do in a case of 
drowning/' in the appendix on page 332. Efforts to restore 
persons from suffocation by drowning, or from any other cause, 
should be continued for a long time, even though no signs of 
life are apparent. 

Effects of alcohol on the lungs.— The tissues of the body, 
when in health, possess, in large measure, the power of resisting 
disease. This power is greatly diminished in those who have 
formed the habit of drinking alcoholic liquor. This lessened 
power of resisting disease is very marked in lung tissue. Those 
who are in the habit of drinking alcoholic liquor are more liable 
to have pneumonia and consumption of the lungs, and are less 
likely to recover from these diseases than those who do not 
drink alcoholic liquor. 

Effects of alcohol on growth.— The cells of a child's body 
are putting forth great effort in order to grow and increase in 
number. To do this the child requires a sufficient supply of 
oxygen, food, pure water, exercise, rest, and sunshine. Suc- 
cessful growth can take place only when the protoplasm of the 
cells is healthy and vigorous. Anything that lessens the activity 
of the protoplasm interferes with the proper growth and de- ' 
velopment of the body. 

It is well known that alcohol, even when weakened very much 
by the addition of water, has a harmful effect upon the activity 
of protoplasm in the cells of both plants and animals. This 
harmful effect has been observed so often that alcohol is called 
a protoplasmic poison. 



140 PHYSIOLOGY FOR YOUNG PEOPLE 

The protoplasm in cells of the tissues of growing children is 
easily injured. Alcoholic liquor in any form, and even in small 
amounts, is injurious to children and growing persons because 
it hinders growth and retards both physical and mental develop- 
ment. 

SUMMARY 

1. The trachea divides into two branches, and the bronchial tubes divide 
until they end in small air sacs. 

2. Tiny capillaries are fitted into the walls of the air sacs. 

3. When we inhale, the chest becomes larger, the lungs expand, and 
air passes in. 

4. When we exhale, the chest becomes smaller and its wall presses on the 
lungs. Air is then forced out. 

5. We should breathe through the nose, and not through the mouth. 

6. The larynx contains the vocal cords. 

7. The opening between the vocal cords is called the glottis. 

8. Vibrations of the vocal cords cause vibrations of air, and vibrations 
of air beat upon the ear and cause sounds. 

9. As blood is flowing along the capillaries in the air sacs, oxygen goes 
from the air to the blood, and carbon dioxide goes from the blood to the 
air. 

10. As the blood is flowing along the capillaries of the tissues, oxygen 
goes from the blood to the cells, and carbon dioxide goes from the cells 
to the blood. 

11. Too little oxygen, or. too much carbon dioxide, in the air we breathe 
impairs the health. 

12. Living rooms should be ventilated at all times, and should be kept 
as free as possible from dust. 

13. Every one should spend part of the day in the open air and sunshine. 

14. Alcohol weakens the lungs, making them more liable to contract 
disease and less liable to recover from it. 



CHAPTER XI 
THE SKIN AND THE KIDNEYS 

Our bodies are protected by a smooth, pliable covering which 
we call the skin. It consists of two parts. The outer part is 
called the epidermis, or scarf- 
skin; the inner part is called 
the dermis, or true skin. 

The epidermis.— If you 

have ever examined a blister 

you have probably noticed 

that the skin is puffed out 

and that there is water below 

it. It is, however, only the 

epidermis that is puffed out. 

The dermis is below the water. 

The epidermis is made up of 

layers of cells placed one on 

another. The cells of the 

outermost layer are always wearing out and being shed 

from the surface in the form of flat, lifeless scales. The cells 

of the layer next to the dermis are always increasing in number 

by division and furnishing new cells to take the place of those 

that are shed. 

141 




a, true skin; b, b, layers of 

SCARF-SKIN 
(Magnified) 



142 



PHYSIOLOGY FOR YOUNG PEOPLE 



The cells of the outer layers of the scarf-skin have no feeling, 
for these layers contain no nerves. If you prick these outer 
layers with the point of a needle you will feel no pain. More- 




NERVES AND BLOOD TUBES IN TRUE SKIN 
(Magnified) 

over, you will see no blood, unless the point of the needle passes 
on into the true skin, for the scarf-skin contains no blood tubes. 

If the scarf-skin is rubbed or pressed day after day it will 
become thicker. For this reason the skin on the palm of the 
hand and the sole of the foot often becomes quite thick and 
hard. This explains why boys that go barefoot in the summer 
can walk over rough, and even stony, ground without hurting 
their feet. 

In the inner layers of the cells of the epidermis there are 
tiny granules of coloring matter. It is this coloring matter 
that causes differences of tint in individuals, and of color in 



THE SKIN AND THE KIDNEYS 143 

races. In the skin of white people there is very little coloring 
matter; in the skin of the negro there is a great deal. 

The dermis. — The dermis lies below the epidermis. In the 
dermis there are both blood tubes and nerves. The surface of 
the dermis is not smooth and even, but rises up into the epi- 
dermis in small elevations called papillce. These papillae vary 
in shape and size in different parts of the body. In the palms 
of the hands and the soles of the feet they are arranged in rows, 
forming ridges and furrows that can be seen with the naked eye. 
The picture on page 141 shows how the cells of the epidermis 
fill in the spaces between the papillae, and also form a smooth 
layer above their summits. 

The papillae contain capillaries and nerves. The nerves end 
in little knobs, and it is by means of these nerve endings that 
we feel everything that touches us. The dermis is very sen- 
sitive because of its many nerve endings, and if the epidermis 
is removed, the uncovered place wall smart w r ith pain. If you 
have a blister on your hand, it does not hurt until it breaks. 
The epidermis is then removed and the dermis is exposed. 

There are so many blood tubes in the dermis that you cannot 
prick it with the point of a fine needle without puncturing one 
or more tubes and causing blood to flow. The small arteries 
coming from the interior of the body divide into networks of 
capillaries near the surface of the dermis. The capillaries are 
especially abundant in the papillae. They lie in the dermis and 
extend up to, but not into, the epidermis. 

Some papillae are shown in the sketch on the opposite page. 



144 



PHYSIOLOGY FOR YOUNG PEOPLE 



Some of them contain capillary blood tubes, and one contains 
an ending of a nerve. 

Nerves end in the skin in two principal ways. Some nerves 
end in the dermis in little swellings or knobs, mainly in the 




SECTION OF SKIN 

1. Sweat gland. 2. Muscle. 3. Duct. 4. Pore. 5. Hair. 6. Oil glands. 
7. Papilla, showing capillaries 

papillae. Other nerves divide in the dermis just beneath the 
epidermis. From these nerves, fine delicate fibrils pass upward 
and end in the lower layers of the epidermis. Nerve endings 
are especially abundant in the tip of the tongue, the skin on the 



THE SKIN AND THE KIDNEYS 1 15 

palms and the tips of the fingers, the tip of the nose, and other 
parts specially sensitive to touch. This explains why the 
sense of touch is so acute in the finger-tips and other highly 
sensitive parts. 

Perspiration. — On a warm day, water, or perspiration, as 
we call it, comes out of the skin and collects in drops on the 
face and other parts of the body. This is called sensible per- 
spiration, because it can be observed. But whether the day is 
w r arm or cold, whether we are awake or asleep, we are per- 
spiring all the time. Day and night, perspiration slowly rises 
from the surface without our knowledge. This is called in- 
sensible perspiration, because it cannot be observed. 

The perspiration we see is a colorless, salty liquid. It is 
chiefly water, and contains a small amount of common salt, 
and also a little of such waste matters as carbon dioxide and 
urea, which pass out of the body in this way. 

The amount of perspiration from an adult in twenty-four 
hours is said to be about two pounds. But, of course, the 
quantity varies greatly with circumstances. 

Sweat glands. — The skin of nearly all parts of the body con- 
tains very fine tubes, the inner ends of which are coiled into 
knots. After leaving the knots, the tubes twist into spirals 
and afterward open on the outer surface of the skin. The 
part of a tube that forms the knot is called a sweat gland; the 
rest of the tube is called a sweat duct; the opening on the sur- 
face is called a pore. The cells in the knots, or glands, take 
from the blood the material that makes the perspiration, which 



146 



PHYSIOLOGY FOR YOUNG PEOPLE 




then passes along the sweat ducts and comes out on the surface 
of the skin through the pores. It is estimated that there are 
more than two millions of these pores on the surface of the body. 
Hair. — In the dermis are many little pockets or sacs, called 
hair follicles. Hairs grow out of these pockets. In the lower 
animals the hair is stiff and coarse; in human 
beings it is soft and fine. Here is a picture of 
a bit of human hair as it looks through a mag- 
nifying glass. You can see from it that the 
cells that form the hair overlap like fish scales. 
Hair does not look much like skin, yet it is 
made up wholly of changed cells of scarf-skin. 
They are pressed together lengthwise and grow 
only in length. 

From the bottom of each hair follicle there runs a tiny muscle 
that ends in the outer part of the true skin. Find it in the pict- 
ure on p. 144. When this little muscle contracts, it makes the 
hair stand more erect. When the hairs on a cat's back bristle 
at the sight of a dog, it is because the little muscles controlling 
the hairs have contracted and pulled the hairs erect. 

The bottom of each little hair follicle is the top of a papilla, on 
which the root of the hair rests. The hair gets its nourishment 
from the network of capillaries in the papillae. The growth of 
a hair takes place at the root only. Here the cells are constantly 
increasing in number by division. As a result, the older cells 
are pushed outward and the hair increases in length, but not in 
circumference, 



BIT OF HAIR 

(Magnified) 



THE SKIN AND THE KIDNEYS 147 

Small granules of coloring matter give the hair its color. 
When the coloring matter disappears the hair becomes gray. 

In a hair are numerous little spaces into which air make- its 
way from the ends of the hair. The air in gray hairs gives them 
a silvery appearance. 

Hair protects the head from the direct rays of the sun in hot 
weather, and prevents too rapid loss of heat in cold weather. 

The skin of the top of the head is called the scalp. The 
cells of the outer layer of the scalp are shed from time to time, 
just as cells are shed from the surface of the skin in other parts 
of the body. These scalp cells become entangled in the hair, 
but are easily removed by brushing. 

The hairs that grow on the edge of each evelid are called 
eyelashes. The eyelashes catch particles of floating dust that 
might get into the eyes; and they also act as a screen from 
the bright sunlight, Thus, in two ways, they protect the 
eyes. 

The oil glands. — In health, the hair is kept soft and glossy 
by means of oil. The oil is made by oil glands lying beside 
the root of the hair. It is then poured out upon the root of the 
hair and gradually finds its way to the surface of the skin. 
Each hair has one or more of these glands. Find the oil 
glands in the picture on page 144. 

The nails. — The nails that protect the ends of the fingers 
and toes are developed from scarf-skin. They are cells of the 
epidermis in a different form. The edge of the nail, except at 
the free end, rests in a groove made by the skin. Growth takes 



148 PHYSIOLOGY FOR YOUNG PEOPLE 

place at the root, and also from the bed, or matrix, on which 
the nail rests. 

When the nails are kept clean and well trimmed they are 
beautiful ornaments. Biting the nails injures them. It is a 
habit that is frequently formed in youth and is sometimes quite 
difficult to give up. The best remedy is to keep the nails cut 
very short until the habit is overcome. 

Uses of the skin. — You have already learned that one use 
of the skin is to protect the body, and that another is to provide 
for the escape of some waste matter through the perspiration. 
Still another very important use of the skin is to regulate the 
heat of the body. This heat, you remember, is produced by 
oxidation in the tissues. Oxidation takes place in the cells of 
all the tissues, but chiefly in the cells of the muscles and the 
glands. The heat is then distributed all through the body by 
means of the blood, and thus the temperature of the various parts 
is equalized. The heat of the skin, for example, depends upon 
the amount of blood flowing through it. When the arteries of 
the skin are dilated and contain much blood, the skin is warm; 
when they are contracted and contain less blood, the skin is 
cooler. 

While heat is being constantly produced in the body, heat is 
also being lost from the body all the time. A part of this loss 
takes place in the act of breathing. The cool air breathed in 
becomes warmer in the lungs ; and, when it is breathed out, 
heat is lost from the body. Furthermore, the air surrounding 
the body is usually cooler than the body. Consequently, heat is 



THE SKIN AND THE KIDNEYS 149 

lost from the skin in the same way that heat is lost from a piece 
of iron that is taken from a furnace and allowed to cool in the 
open air. When the body is in a state of health, the production 
and the loss of heat are so regulated that the temperature of the 
body remains the same. 

When your body is becoming heated through running or 
other work, the arteries of the skin dilate and contain more 
blood. But the heat also stimulates the sweat glands to pour 
out abundant perspiration on the skin to cool the body. If 
you sprinkle water on a floor on a hot day, the air in the room 
becomes cooler afterward. The air becomes cooler because 
some of its heat is used to change the water into vapor, or 
evaporate it. The cooling of the body by perspiration is caused 
in the same way. Some of the body's heat is taken from it and 
used to change the perspiration into vapor. 

On the other hand, when your body is surrounded by cold 
air, the muscles in the arteries of the skin contract, so that the 
arteries become smaller and hold less blood. More of the 
blood then remains in the interior of the body, and less comes to 
the skin, where heat would be lost rapidly. At the same time 
the sweat glands become less active, and little perspiration is 
evaporated from the skin. 

The power of the body thus to regulate heat is so great 
that the temperature of the body is almost the same in summer 
and in winter. It scarcely varies, whether we live in arctic 
regions, where the temperature may be 50° F. below zero or 
lower, or in the tropics, where it may exceed 115° F. The 



150 PHYSIOLOGY FOR YOUNG PEOPLE 

temperature of the body, under ordinary circumstances, is 
98.6° F. 

In our bodies, the greatest loss of heat occurs through the 
skin. It is estimated that the loss through the skin is nearly 
77 per cent, of the entire loss of heat from the body; that the 
loss through the lungs is a little more than 20 per cent, of the 
entire loss; and that nearly 3 per cent, is lost in other ways. 
These figures show how important the work of the skin is in 
regulating the heat of the human body. 

On the other hand, the dog, which perspires but little, loses 
a much larger amount of heat from the lungs. The panting of 
the dog when he is overheated is his way of cooling off. He 
breathes in a large amount of air, which becomes heated and 
takes heat from the body as it is breathed out. He also puts 
out his tongue, and loses some heat by the evaporation of 
moisture from its surface. 

Mammals and birds are called warm-blooded animals. In 
each kind of these animals the temperature of the healthy body 
remains the same whether the surrounding air is cold or warm. 
The normal temperature of the human body, as we have learned, 
is 98.6° F.; the temperature of the dog is 102° F.; and the tem- 
perature of the swallow is 111° F. As a rule, the more active an 
animal is, the higher is its usual temperature. These active 
animals consume a large amount of food, and produce a large 
amount of heat. They lose, however, a sufficient amount of 
heat to keep the temperature of the body uniform. 

The temperature of invertebrates, so far as is known, and of 



TIIK SKIN AND THE KIDNEYS 151 

such vertebrates as reptiles, frogs, and fishes, varies with the 
temperature of the surrounding air, soil, or water. Such ani- 
mals are called cold-blooded animals. The temperature of 
their bodies is usually only a very little above the temperature 
of what surrounds them. Many of these animals are sluggish, 
and consume only a small amount of food. Consequently they 
produce only a small amount of heat. 

Bears, woodchucks, and some other warm-blooded animals, 
pass the winter in a torpid state, and are said to hibernate. The 
temperature of the body becomes nearly as low as that of the 
surrounding soil in which they burrow; breathing almost ceases; 
and the heart beats very feebly. In this condition very little 
food is needed, and that is obtained from the fat of the body. 
In the fall these animals are fat, but in the spring they are lean. 
A mammal, such as the woodchuck, which lives on green vege- 
tables, could not survive a northern winter if it did not hiber- 
nate, and thus avoid the necessity for a continuous supply of its 
accustomed food. 

^Yhen an animal, such as a rabbit, is entirely covered with a 
thick varnish, it dies in a short time. It was formerly thought 
that this happens because poisonous matter which should be 
discharged through the skin is shut up in the rabbit's body. It 
has now been proved beyond a doubt that death in these cases 
is caused by a rapid loss of heat, and not from poisoning by 
waste matter, for varnished animals wrapped in cotton wool 
remain well and suffer no bad effects. 

It has been shown also by experiment that the whole surface 



152 PHYSIOLOGY FOR YOUNG PEOPLE 

of the human body can remain, for eight or ten days, covered 
with a layer that allows nothing to get through it, and yet suffer 
no injury. There is on record a story of a small child that 
was gilded to represent an angel. In a few hours the child died, 
but death was due in all probability to some poison in the 
material used for gilding. 

Bathing. — The skin cannot be healthy and do its work well 
unless it is clean. A small amount of waste matter is left on 
the surface of the skin after the water in the perspiration has 
evaporated. This becomes mixed with oily matter from the 
oil glands, and with scales from the outer layer of the epidermis. 
These soon form a coating that tends to irritate the skin and 
gives rise to unpleasant odors. 

Those accustomed to take a daily morning bath think it very 
little trouble and are uncomfortable without it. It requires 
only a few minutes and the labor is trifling. Every one in 
ordinary health should take a daily bath. Water, soap, a 
sponge, a basin, and a towel are all that are needed for a sponge 
bath. 

Should the water be warm or cold ?— No rule can be given 
that is suitable for every one. Warm water softens the oily 
scales on the surface of the epidermis, and, used with soap, is 
an important aid to cleanliness. Warm water also causes the 
arteries of the skin to relax and become larger, so that a large 
amount of blood comes to the surface. A warm bath gives rise 
to a pleasant, comfortable feeling; but if the bath is prolonged, 
a feeling of depression and weakness follows. Warm baths, 



THE SKIN AxND THE KIDNEYS 153 

like heat of any kind, weaken the muscles in the arteries of the 
skin and lessen their power to contract. As these arteries thus 
remain too large, they contain too much blood, and heat is lost 
rapidly from the body if one is exposed to cold. For this reason, 
a person who goes into cold air after taking a warm bath is 
liable to take cold. 

A warm bath at bedtime is soothing. If the muscles are sore 
and ache after a day of hard labor or other severe exertion, 
nothing is more soothing than a warm bath. It causes the 
arteries of the skin to dilate; and, since much of the blood is 
withdrawn from the muscles, the aching and soreness vanish 
speedily. Those who suffer from difficulty in getting to sleep 
will find that a warm bath at bedtime often invites refreshing 
slumber. 

A warm foot-bath containing mustard is useful in cases of 
convulsions in children. A tablespoonful of mustard should 
be put into a quart of warm water, and the feet should be placed 
in it while the child is lying on the bed. The mustard bath 
should be continued until the skin of the feet and ankles is well 
reddened. 

A cold bath causes the muscles in the walls of the arteries of 
the skin to contract. These arteries then become smaller and 
force part of the blood away from the skin to the interior of 
the body. For this reason we feel chilly and shiver when we 
first get into cold water. In a few minutes the arteries of the 
skin relax, blood returns to the skin, and gives rise to an agree- 
able feeling of warmth and comfort. The bath should be ended 



154 PHYSIOLOGY FOR YOUNG PEOPLE 

before this feeling passes away, and should be followed by a 
brisk rubbing of the skin. A cold bath acts as a tonic and 
produces increased vigor of both body and mind. Cold baths 
tend to stimulate circulation and to increase the oxidation of 
food in the tissues of the body. Increased appetite and in- 
creased excretion of waste follow. 

In most cases it is best to use cold water for bathing. When 
warm water is used for the first part of a bath, it may be changed 
for colder water during the latter part. A bath is said to be 
cold if the temperature of the water does not exceed 65° or 70° 
F. Very cold baths should be used only by those that are in 
robust health. 

Some persons complain of catching cold after taking a bath, 
especially in cold weather. This is because they fail to dry 
the skin properly. Two towels should always be used after a 
bath: the first one to wipe off the water, and the second one to 
rub the skin until it is thoroughly dry and warm. If the skin 
remains moist, the evaporation that follows chills the surface of 
the body and tends to produce a cold. 

Persons that take cold easily should bathe the shoulders, 
chest, neck, and face with cold water every morning. The skin 
should then be rubbed briskly until it is thoroughly dried. 

Bathing the head. — The scalp and hair should be washed 
thoroughly with soap and water at least every two weeks. 
When this is not done, scales and dust collect and interfere with 
the health of the hair and the scalp. 

Water that is quite warm should be used first to soften the 



THE SKIN AND THE KIDNEYS L55 

oily scales, and then cold water should be used. Great care 
should be taken to dry the hair thoroughly after washing it, 
for the danger of taking cold after bathing the head will thus 
be avoided, even in cold weather. 

Swimming. — Swimming is healthful exercise, but many per- 
sons stay in the water too long at one time. Twenty minutes 
or half an hour is quite long enough. No one should go into 
deep water when he is very tired, or when he is warm and is 
perspiring freely, for at such times he is more liable than usual 
to be seized with cramps. 

Colds. — Colds are most frequent during spring and fall. At 
such times there are frequent changes of temperature, the air is 
often cool and damp, and winds are common. 

Colds are not due merely to exposure to very cold air or 
frost, else they would be more common in mid-winter and in 
Arctic regions. The more usual causes of taking cold are 
sitting or standing in a draft, going from a warm room to a 
cold one, want of proper protection for the feet, sitting or 
standing still after vigorous exercise while the surface of the 
body is moist from perspiration. The last is a frequent cause, 
for we often take cold after being too warm. 

Another very common way of taking cold is by " catching' ' 
it from some one else who has a cold. Colds are contagious. 
They are often brought home by children that have " caught" 
them by close contact with other children at school. If a cold 
gets into a family it is liable to infect the whole household 
before it stops. The infection is probably carried solely by the 



156 PHYSIOLOGY FOR YOUNG PEOPLE 

breath. Care should be taken to avoid conveying the infection 
from one person to another. Any person with a cold should, 
as far as possible, remain apart from the rest of the family and 
from friends. 

Some persons are more liable than others to take cold, and 
this liability is due generally to a faulty manner of living. 
Those that get very little fresh air because they stay in-doors 
unless the weather is fine; those that live in over-heated houses 
and sleep in rooms with windows carefully closed for fear that 
they may take cold ; and those that overburden themselves with 
clothing, so that they cannot take active exercise without per- 
spiring freely, are liable to take cold from the slightest expo- 
sure. 

An ordinary cold should not be allowed to take its own 
course without treatment. Certain diseases, such as smallpox, 
protect the body against a second attack. But one attack of a 
common cold, especially if it is neglected, renders the body more 
liable to another attack. The common household remedy of a 
hot drink and a hot foot-bath at bedtime is useful in arresting 
or weakening the force of a cold, especially if used at the begin- 
ning of an attack. 

Prevention of colds. — The well-known causes that produce 
colds, should be avoided. Just enough clothing should be worn 
to keep the body warm. If too little is worn the skin may be 
chilled, and we may take cold. If too much is worn, slight 
exertion causes perspiration, the body is kept over-heated and 
becomes sensitive, and so we are liable to take cold on the 



THE SKIN AND THE KIDNEYS 157 

slightest exposure. The common mistake of putting too much 
clothing on one part of the body and too little on another part 
should he avoided. It is unwise to try to prevent a cold in the 
chest by putting on too many wraps, or by wearing chest pro- 
tectors. Too much muffling leads to perspiration, renders the 
chest and the throat more sensitive, and increases the liability 
to take cold. The feet should be protected against cold and 
dampness. 

A part of every day should be spent out of doors. Those 
that are accustomed to be out of doors in all kinds of weather 
seldom take cold. 

Sleeping rooms should be well ventilated. Both day and 
night a window should be sufficiently open to insure thorough 
ventilation. 

Great care should be taken to avoid sitting or standing still 
when the skin is moist from perspiration, unless extra wraps are 
worn while the body is cooling. 

Our climate is changeable. In a few hours we are frequently 
subjected to marked differences in heat and cold. It is im- 
possible to change our clothing every time the weather changes. 
The only way to protect ourselves in such a climate is to keep 
the body in perfect health, so that we may be exposed to rapid 
changes in temperature without any danger of taking cold. 

The daily cold bath is of great value in protecting the body 
against colds, for it strengthens the muscles in the arteries of 
the skin. Exercise of any muscle causes it to become stronger. 
Cold baths exercise the muscles in the arteries of the skin, and 



158 PHYSIOLOGY FOR YOUNG PEOPLE 

give them greater power to contract. Accordingly, when the 
body is exposed to a sudden change in temperature, the muscles 
in the arteries of the skin contract promptly, the arteries be- 
come smaller, less blood comes to the surface of the body, and 
the liability to take cold from exposure is lessened. 

Clothing. — Articles of clothing are usually made from wool, 
silk, cotton, and linen. Clothing does not furnish heat to the 
body. It only retains heat that is made in the body, and so 
keeps it warm. 

Clothing that is loosely woven retains heat better than cloth- 
ing that is closely woven. Loosely woven clothing contains 
a considerable amount of air in the little spaces between its 
fibres, and heat does not pass readily through dry air. 

Again, clothing that absorbs the moisture of perspiration 
into the substance of the fibres retains heat better than clothing 
that does not absorb moisture into the substance of its fibres. 
You remember that heat is lost from the air of a room on a hot 
day when water that is sprinkled on the floor evaporates. In a 
similar manner, heat is lost from the surface of the body when 
moisture evaporates from clothing we wear. If the clothing 
that is next to the body absorbs moisture into its fibres, that 
moisture evaporates slowly, and heat is lost from the body 
slowly. But, if clothing holds moisture largely in the spaces 
between its fibres, and absorbs but little into the substance of 
the fibres, then the moisture evaporates rapidly, heat is lost 
rapidly from the body, and we feel chilly. 

Wool, in both of these particulars, is an excellent article of 



THE SKIN AND THE KIDNEYS 159 

clothing. Woollen garments retain heat well in cold weather 
because they are loosely woven, and hold a considerable amount 
of air in their meshes. Wool is better also than any other 
article of clothing for absorbing moisture into the substance of 
its fibres, and allowing it to evaporate slowly. Those that are 
subject to rheumatism, or that take cold easily, should wear 
woollen garments next to the skin throughout the year. The 
weight of the garment should vary with the season. 

Silk comes next to wool in its power to absorb moisture into 
its fibres. It is therefore an excellent material for undergar- 
ments, especially for those persons that cannot wear wool next 
to the skin. The chief obstacle to the general use of silk for 
clothing is its cost. 

Linen is closely woven, its meshes are small, and contain 
little air. Linen does not absorb moisture into its fibres so 
readily as wool or silk, but holds the moisture more in the 
spaces between its fibres. Consequently, linen garments allow 
heat to escape from the body more rapidly than silk or wool. 
Garments made from linen are more suitable for hot than for 
cold or changeable climates. 

Cotton, too, is closely woven, and does not absorb moisture 
into its fibres so well as wool or silk. It allows heat to escape 
from the body freely. Cotton, therefore, makes cool garments 
for warm climates or seasons. It is cheap and wears well. 
For these reasons it is very generally used for clothing. Cotton 
and linen garments should not be worn next to the skin by 
those that take cold easily or that are subject to rheumatism. 



160 PHYSIOLOGY FOR YOUNG PEOPLE 

because these materials allow too rapid evaporation and cooling 
of the body. 

Waste matter and excretion.— The work of removing 
waste matter from the body is called excretion, and the organs 
that do this are called excretory organs. 

The excretory organs. — The chief excretory organs are the 
lungs, the skin, and the kidneys. You learned that by means 
of the lungs we get rid of carbon dioxide and also of a small 
amount of water in the form of vapor. They are contained in 
the air that we breathe out, and are produced in the body by 
the oxidation of carbohydrate food. 

The tissues of the body are built up from proteid food, which 
always contains nitrogen; and the waste matter that results 
from the breaking down of the tissues also contains nitrogen. 
This waste matter resembles ammonia, and is called urea. If 
this waste matter is allowed to accumulate in the blood and in 
the tissues it acts as a poison. It must be carried out of the body. 

Through the skin we lose, in the form of perspiration, a very 
small amount of carbon dioxide, a trace of urea, and a con- 
siderable amount of water. 

The kidneys are the organs that remove from the blood nearly 
all of the urea that is excreted from the body. 

The kidneys. — There are two kidneys, one on each side of 
the spine. Their upper ends lie behind the lower ribs. 

The kidneys are well supplied with blood. In the picture 
on page 162 you can see that one kidney lies on each side of 
the aorta. A branch of the aorta, called a renal artery, enters 



THE SKIN AND THE KIDNEYS H>1 

each kidney. As the stream of blood flows downward through 
the aorta, a part of it is diverted from the main channel and 
flows into the renal arteries. After circulating in the kidney this 
blood passes out by the renal veins. It flows from the renal 
veins into the vena cava inferior, which returns the blood from 
the lower part of the body to the heart. The kidneys take 




SECTION OF A KIDNEY 



urea and w T ater from the blood as it goes through them. This 
fluid, which is called urine, passes by means of ducts, named 
ureters, to the bladder, where it is stored until it is expelled 
from the body. Only a small part of the blood in the aorta 
passes through the kidneys each time it circulates. The kid- 
neys do not remove all the urea from the blood, but, by con- 
stantly removing part, they keep this waste matter from accu- 
mulating to an amount that w T ould be harmful to the body. 

This picture shows the appearance of the cut surface of a 
kidney after it has been divided. The kidney substance, which 



162 PHYSIOLOGY FOR YOUNG PEOPLE 

appears in the picture to be striped and marked with many fine 
lines, is composed of a mass of tiny blood tubes and of other 
tiny tubes that carry water. This water has been taken by the 



3~#J 




KIDNEYS IN THEIR POSITION 
1. Kidney. 2. Aorta. 3. Inferior vena cava. 4. Uretur. 5. Bladder 

kidneys from the blood, and contains in solution the urea that 
must be removed from the body. 

Effects of alcohol on the skin.— Alcohol evaporates rapidly 
when applied to the skin, and gives rise to a sensation of cool- 
ness. It also hardens the outer layers of cells in the epidermis. 



THE SKIN AND THE KIDNEYS 163 

When taken internally, alcohol affects the skin chiefly by its 
action on the nerves which end in the small arteries of the 
dermis. These nerves end in muscles that are wrapped in a 
circular manner around the blood tubes and form part of their 
walls. Nerves ending in these muscles control them, and when 
the circular muscles in the w T all of an artery contract, the size 




A KIDNEY 

of the artery is decreased, and it contains a smaller amount 
of blood. When the circular muscles relax, the artery dilates 
and contains a greater amount of blood. Alcohol lessens the 
control of the nerves over the muscles in the w r alls of the 
arteries. The muscles relax, and the arteries then contain 
more blood. 

After even a moderate drink of alcoholic liquor the skin of 
the face becomes flushed and warm, because the little blood tubes 
of the skin are dilated and contain more blood than usual. If 
these tubes are kept dilated by continued drinking they may in 



164 PHYSIOLOGY FOR YOUNG PEOPLE 

time become permanently dilated and give the face a permanent 
reddish color. 

Effect of alcohol on the temperature of the body.— As the 
blood tubes of the skin dilate under the influence of alcohol, a 
larger amount of blood than usual comes near the surface of 
the body and, in cold weather, is cooled by the surrounding air. 
The action of the sweat glands is increased at the same time 
and the temperature is reduced by increased evaporation from 
the skin. In this way the heat of the body is lost more rapidly 
than it would be if no alcohol were taken. 

The extra amount of blood contained in the dilated blood 
tubes makes the skin feel warmer because it warms the endings 
of the nerves in the skin. It is this feeling of warmth that 
deceives those that drink alcoholic liquors, and gives rise to the 
false notion that alcohol makes the body warmer on a cold day. 
The fact is that the body is losing heat faster than it should. 
If a large amount of alcohol is taken the loss of heat may be 
very great. 

Effects of alcohol on the kidneys.— The effects of alcohol 
on the kidneys resemble closely its effects on the liver. As a 
result of the irritant action of alcohol on the kidney cells they 
may swell, and, if the irritation is continued, their protoplasm 
may change more or less completely to fat. The connective 
tissue cells also of the kidneys may be affected by the continued 
irritation of alcohol. These cells may increase in number, 
press upon the other kidney cells, and injure or even destroy 
them. These changes interfere very seriously with the import- 



THE SKIN AND THE KIDNEYS L65 

ant work of the kidneys in removing from the blood urea, which 
would act as a poison if it were to accumulate in the blood. 

The following letters and statement are submitted to show 
that it is safer in both cold and hot climates not to drink alco- 
holic liquors. 

New York, June 7, 1907. 

Dear Sir: — According to the reports of Dr. Nansen and the Duke 
of the Abruzzi, both of whom reached high latitudes on the polar 
ice, no alcoholic stimulants were used on their sledge trips. 

In our two years' stay in the Arctic, our sledge parties made 
nearly four thousand miles across ice and snow under the peculiarly 
trying conditions of the polar regions. We never carried any alco- 
holic stimulants as part of our sledge rations, believing them to be 
detrimental. 

Smoking was allowed and indulged in by a large number of the 
men. They usually lit their pipes when they had crawled into 
their frozen sleeping bags after the day's hard work of hauling and 
lifting the heavy sledges and driving the capricious dogs was over. 

From observation on many sledge journeys, I have come to the 
belief that the use of tobacco is harmful also, and that men addicted 
to its use cannot endure so much hardship as those who are not. 

Yours truly, Anthony Fiala, 

Commanding Ziegler Polar Expedition of 1903-1905. 

New York, June 18, 1907. 
Dear Sir: — In reply to your recent letter, I would say that during 
the summer months, in interior Labrador, we experienced a great 
variety of temperature, ranging sometimes from nearly ninety 
degrees at midday to below the freezing point at night and, as fall 
approached, well down to zero. Protracted storms of rain and 



166 PHYSIOLOGY FOR YOUNG PEOPLE 

sleet and snow were frequent; and often, for days and nights to- 
gether, myself and men were compelled to work and sleep in water- 
soaked garments. Each man carried a pack of considerably over 
a hundred pounds, and the physical strain was tremendous, while 
for a good part of the time our rations were scant. 

During my winter journey of two thousand miles with dogs and 
snowshoes, it was not unusual to have, even at midday, a tempera- 
ture of fifty degrees below zero. Often we slept in snow igloos 
or on the open snow fields with no fire with which to warm our- 
selves. 

Had I used, or permitted my men to use, alcoholic liquors as a 
beverage, I am confident my expedition would have been a failure. 
My observation is that a man taking even one small drink of liquor 
in the morning is incapacitated for his day's work under the condi- 
tions that we faced. I may go even further, and say that one to 
be fit should abstain absolutely from the use of alcohol for weeks 
or even months before entering upon such an expedition. 

Yours very truly, DlLLQN Wallace . 

In a large American Medical work, Twentieth Century Prac- 
tice of Medicine, Dr. Wolfred Nelson says, under " Yellow 
Fever," in Vol. XX, page 448: "The moderate drinker, as a 
rule, is lost from the start. The liver in such cases plays a most 
important role. The use of alcohol in any form by newcomers 
within the tropics is a very pernicious habit. The climate alone 
taxes the liver, and alcohol adds to the trouble. If one must 
live in the tropics, or try to live there, let total abstinence be 
made a rule of life." 



THE SKIN AM) THE KIDNEYS 167 

SUMMARY 

1. The skin consists of two parts: epidermis and dermis. 

2. The outer cells of the epidermis continually fall off, and the cells of 
the lowest layer divide to form new cells. 

3. Papillae in the dermis contain endings of nerves, by which we feel. 

4. Nerve endings are most numerous in the finger-tips and other parts 
that are most sensitive to touch. 

5. The dermis is supplied with a large number of blood tubes. 

6. Perspiration is secreted in the sweat glands. 

7. Hair is made up of changed cells of the epidermis. 

8. A hair rests on a papilla at the bottom of a follicle. 

9. Oil glands beside the roots of the hair furnish oil which keeps the 
hair soft and glossy. 

10. The nails are formed from changed cells of the epidermis. 

11. The skin protects the body, allows waste matter to escape in per- 
spiration, and regulates the heat of the body. 

12. A warm bath should be taken at night. 

13. A cold bath should be taken in the morning. 

14. A cold bath acts as a tonic for those who can take it. It improves the 
health and protects against " catching cold." 

15. Wool is the best article of clothing in cold weather. 

16. Alcohol lessens the control of the nerves over the muscles in the 
walls of the arteries in the dermis. 

17. Owing to the increased amount of blood in the skin, the drinking 
of alcohol lowers the temperature of the body on a cold day. 

18. Alcohol injures the kidney cells and the connective tissue that holds 
them together. 



PART III— THE FUNCTION OF MOVEMENT 



CHAPTER XII 



PLANT AND ANIMAL MOVEMENTS 



The power to move. — Only living things have the power to 
move. Things without life stay in the same place and position 

until made to move by some out- 
side force. A ball when struck 
• with a bat will fly through the 
air, but it must be struck before 
it will move. 

But living things have in 
themselves the power to move. 
They all have the power to 
move a part of the body, as 
a leaf, a hand, or a foot. Ani- 
mals and a few plants have 
the power also to move from 
place to place. 

Some movements of plants. — Plants can move different 
parts, as a root, a leaf, or a stem. On a sunny morning, the 
leaves and growing top of a sunflower turn toward the east to 
face the sun, and follow it throughout the day, facing toward 
the west in the evening. The stem of a young plant grows 

168 




STEMS GROWING UPWARD 



PLANT AND ANIMAL MOVEMENTS 1G9 

away from the centre of the earth and the root grows toward 
it. If a flower pot that contains a growing plant a few inches 
in height is placed on its side, the end of the stem will turn 




LEAF OF SENSITIVE PLANT BEFORE IT 
IS TOUCHED 




slowly and grow upward, and the end of LEAp OF A SEXSITIVE 
the root will turn and grow downward. PLANT AFTER IT IS 

TOUCHED 

The sensitive plant shows a remarka- 
ble example of plant movement. It has little leaves arranged 
in pairs on four separate stems. If one of the leaflets is 
touched, all the leaflets of that leaf will quickly fold together 
in pairs, and the leaf-stalk will turn downward and remain 
in a drooping position for some time. 

Certain movements of some plants are called sleep move- 
ments, because they usually take place in the evening and in 
the morning. In the evening the leaves of the clover fold them- 



170 



PHYSIOLOGY FOR YOUNG PEOPLE 



selves together. In the morning these leaves take again an 
open position. Other familiar sleep movements are the closing 
at night and the opening in the morning of such flowers as the 
tulip, crocus, dandelion, and water-lily. 

Locomotion. — The power of living things to move from 
place to place is called locomotion. The animals that you 




A PAPER NAUTILUS 

(s) Siphon 



know best move about freely from place to place; they must 
do so in order to find their food. Yet there are animals, such 
as oysters, that can move about for only a short time. Very 
soon they settle on some shell or rock, and then have no power 
to move away from it; they do not have to move about to find 
their food, but get it in one spot. There are, moreover, tiny 
plants that move from place to place in liquids. Some of these 
are the disease germs, called bacteria, which move about in 
milk, water, or blood, though they are so small that they can 



PLANT AND ANIMAL MOVEMENTS 171 

he seen only with a microscope. Many of these little plants 
move by means of little hair-like fibrils, called cilia, that pro- 
ject from their surfaces. 

Swimming. — One simple form of animal locomotion is the 
sort of swimming that is seen in the movements of such animals 
as the cuttle-fish and the nautilus. They fill a cavity in the 
front part of the body with water, and then quickly expel this 
water through a funnel, which is usually called a siphon. As 
this stream of water is forced against the surrounding water, 
the animal is propelled rapidly in the opposite direction, that is, 
backward. 

The lobster swims backward by striking the water with his 
tail as he bends it downward and then forward under his body. 

The feet and limbs of many animals are especially suited to 
swimming. Ducks, geese, swans, frogs, otters, muskrats, and 
beavers have some, or all, of their feet webbed, and use them 
as paddles with which to push against the water. 

Of all organs of locomotion the best adapted to swimming 
are the tails and the fins of fishes. A fish bends its tail to 
the right side of the body and strikes back against the water in 
straightening the tail. Then it bends the tail to the left side 
and strikes back. This powerful push against the water, as the 
fish forces its tail back straight after bending it to one side, 
sends the fish rapidly along. The force with which the salmon 
strikes the water with its tail is so great that it can swim at the 
rate of twenty-four feet a second, and can leap out of the water 
over cascades twelve or thirteen feet high. 



172 



PHYSIOLOGY FOR YOUNG PEOPLE 



Columbia River salmon leave the Pacific Ocean in the spring, 
and swim up the Columbia and its tributaries in order to spawn, 




140* 150* 120° IIP* 100° 90* 60° 7Q° 60" 50 5 4<? 3V 



MAP SHOWING FLIGHT OF AMERICAN GOLDEN 

PLOVER SO FAR AS DETERMINED 

From the Year Book of the Department of Agriculture for 1903 

sometimes more than a thousand miles; for they are found that 
far away from the sea in Salmon River, as it winds among the 
Sawtooth Mountains of Idaho. 



PLANT AND ANIMAL MOVEMENTS 173 

Flying. — As fishes swim by pushing against the water with 
fins and tails, so birds and insects fly by pushing against the air 
with wings. The stroke of the wing against the air keeps the 
body up and also sends it forward. The swiftest flyers among 
insects are bees, wasps, and dragon-flies; among birds,* the 
swiftest are pigeons, swallows, wild ducks, hawks, and falcons. 
A homing pigeon has been known to make a flight of seven 
hundred miles in thirteen and a half hours. Some birds cover 
in their yearly travels as much as twenty thousand miles. The 
common night hawk flies as far north in spring as Alaska, where 
it makes its nest and rears its young. As winter comes on it 
flies as far south as Patagonia. The American golden plover 
nests on the shores of the Arctic, and on islands in that ocean, 
and winters in southern Argentina. 

Crawling. — Another form of locomotion is crawling. In 
swimming, the animal pushes against the water; in flying, the 
animal pushes against the air; in crawling, the animal pushes 
against the earth, or whatever other surface it may be crawling 
on. 

The earthworm crawls by means of very small bristles. 
These bristles can be pushed out from the body and fixed in 
the ground like little pins. The w^orm can then push ahead 
its forward part, or draw up its hinder part. 

Snakes crawl by means of shields on the under surface of 
their body, the edges farther from the head being movable. 
The snake moves these edges out from its body, grips the sur- 
face over which it is moving, and pushes itself along. 



174 PHYSIOLOGY FOR YOUNG PEOPLE 

Walking and running. — Walking and running are brought 
about by a backward push against the surface that the feet are 
treading on. If you look at a footprint in moist sand you will 
see that the pressure is made just before the toes are raised, 
for the footprint is broken at the toe. 

Organs of movement.— From this study of movement you 
have learned that different animals have organs of different 
shapes with which to move from place to place. The fin, the 
wing, and the foot are suited to the water, the air, and the earth. 
Nature adapts the size and shape of an organ to the work it has 
to do. In the higher animals these organs of movement are of 
different shapes and sizes, but they are made up of the same 
kinds of material. 

Muscles. — In - animals made up of different kinds of tissue 
each kind has its special work. In such animals the tissue that 
has for its special work the producing of movement is muscle 
tissue. This tissue in an animal does not consist of one mass, 
but of different bundles, each of which is called a muscle. Each 
of these muscles has to do only with movements of its own 
part of the body; one muscle, or set of muscles, moves a 
foot; another muscle, or set of muscles, moves the hand, and 
so on. 

Bones. — The muscles that produce most of the familiar move- 
ments of animal bodies are fastened at their ends, to solid parts. 
The muscles pull on these solid parts and produce movements. 
In animals that have a spinal column these solid parts are called 
bones. They lie within the body, and the principal muscles lie 



PLANT AND ANIMAL MOVEMENTS 175 

on them. In insects, such as flies and bees, in crabs, lobsters, 
and many other animals, the hard part of the body is on the 
outside, and the muscles that produce movement are fastened 
to this hard part and lie within it. 

The controlling organ in movement.— In order that 
muscles in the same body may work together harmoniously 
and each do just the amount of work that is required, they need 
some controlling organ. In animals that move by means of 
muscles, there are nerves that control these muscles and regu- 
late their movements. 

SUMMARY 

1. Only living things have the power to move. 

2. Plants move their leaves, stems, and roots. 

3. The stem of a young plant grows away from the centre of the earth 
and the root grows toward it. 

4. The leaves and leaf-stalks of a sensitive plant move quickly if it is 
touched. 

5. Some movements of the leaves of plants are called "sleep move- 
ments." 

6. Most animals and some plants have the power of locomotion. 

7. The nautilus and some other animals move backward by forcing a 
stream of water against the surrounding water. 

8. The lobster swims backward with its tail. 

9. Many animals have webbed feet for use as paddles in swimming. 

10. A fish swims by pushing against the water with its tail and fins. 

11. Salmon sometimes swim up rivers a thousand miles or more to 
spawn. 

12. Birds and insects fly by pushing against the air with their wings. 

13. In crawling, walking, or running, an animal pushes against the 
earth, or whatever it is moving over. 



176 PHYSIOLOGY FOR YOUNG PEOPLE 

14. It is the function of muscle tissue to produce movement. 

15. Many muscles are attached to solid parts, and pull on them to pro- 
duce movement. 

16. In some animals the solid parts are inside the body, in others the 
solid parts are on the outside of the body. 

17. The movements of muscles are controlled by nerves. 



CHAPTER XIII 
THE BONES 

Bones as organs of movement.— Though there is no power 
of movement in bone as there is in muscle, a great many of the 
movements of the body are caused by the pulling of one bone 
toward another, or away from another, by the muscles that are 
fastened to the bones. Muscles pull the bones this way or that, 
according to the needs of the animal. 

Bones as the framework of the body.— Perhaps you have 
seen the framework of a large building, or, perhaps, you may 
have been in a shipyard, and have seen the framework of a big 
ship that was being built. The framework of a building or a 
ship gives shape to it and also supports its other parts. 

Inside the bodies of the higher animals there is a strong 
framework, which supports and protects the soft tissues and 
gives to each animal its. peculiar shape. This framework is 
called the skeleton, and consists of bones closely joined and 
neatly fitted together. 

In the body of a man the skeleton is made up of two hundred 
bones of many shapes and sizes. There are little irregularly 
shaped bones, as in the wrists; short, slender bones, as in the 
fingers and toes; long bones, as in the arms and legs; rings of 
bone, as in the spinal column; curved plates of bone, as in the 

177 



178 



PHYSIOLOGY FOR YOUNG PEOPLE 




THE FRAMEWORK, OR SKELETON, 
OF THE BODY 



THE BONES 



179 



skull; and flat, broad bones, as in the shoulder 
blades. The picture on the opposite page shows 
how all these different bones are arranged to form 
the framework of the body. 

The spinal column. — The central structure 
in this framework is the backbone, or spinal 

column. It is a strong 
column in the middle 
of the back, and to it, 
either directly or indi- 
rectly, the other parts 
of the skeleton are 
attached. It supports 
the skull at its upper 
end, and the arms at 
a distance from it; the 
ribs are fastened to it 
at the sides; and it 
rests on the hip bones, 
which are supported 
by the legs. 
The spinal column of a grown person consists 
of twenty-six bones, called vertebrce, placed one 
over the other like spools on a string. The 
vertebrae are separated from one another by a 
thin cushion of cartilage, which is elastic and allows the bones 
to move on one another so that the spinal column may be 





FOUR VERTEBRA 




THE SPINAL 
COLUMN 



180 PHYSIOLOGY FOR YOUNG PEOPLE 

bent to some extent in different directions. These cushions 
also prevent injury to the bones of the spine, and to other 
parts of the body, from sudden jars, such as occur in jump- 
ing or falling. 

The vertebrae in different parts of the spine vary in size and 
shape, and are given different names. At the top there are 

seven belonging to the neck and 
called the cervical, or neck, vertebrae. 
Then come twelve vertebrae to which 
the ribs are attached, and these are 
called dorsal, or back, vertebrae. 
Next come five vertebrae which are 
called lumbar, or loin, vertebrae. 
Below the lumbar bones are the sac- 

V VERTEBRA OF THE NECK ^^ Qr gacred bon ^ and ^ coccyX) 

so named because it is supposed to resemble a cuckoo's beak. 

This picture of a vertebra shows a large hole in the centre 
through which a delicate cord passes down from the brain. 
It is called the spinal cord. The small holes in the sides of 
the vertebra are for blood tubes. In the picture of four 
vertebrae on page 179 you can see how the vertebrae are joined 
together, and you can see also the spaces for cushions of 
cartilage between the vertebrae. 

The skull. — Eight plates of bone form the cranium, which is 
a case enclosing the brain. These eight bones are united by 
irregular, saw-like edges that lock firmly together. The joint 
made by these edges is called a suture. 




THE HONKS 



18] 



Fourteen hones of differ- 
ent shapes form the face. 
Two deep depressions, one 
on each side of the nose, 
form sockets for the eye- 
balls. The nose is only 
partly made of bone. Its 
end is composed of cartilage. 

The bones of the crani- 
um and of the face together 
form the skull, which rests 
on the spinal column. 

The picture below shows 





A VIEW OF THE BASE OF THE 
SKULL 



A VIEW OF THE SIDE OF THE 
SKULL 

a view of the base of the skull. 
The large hole is for the spinal 
cord as it extends downward 
from the brain into the cavity of 
the spinal column. 

The ribs and the sternum.— 
There are twelve ribs on each 
side. They are all fastened to 
the spine by means of joints. 
The first seven are called the 
true ribs, and are joined in front 
to the breast-bone, which is also 
called the sternum. The other 
five are called false ribs. The 



182 



PHYSIOLOGY FOR YOUNG PEOPLE 



first three of these are fastened in front by cartilage to the 
rib above. The front ends of the remaining two are free, 
and these are called floating ribs. The joints allow a slight 

movement of the ribs in 
breathing. 

The ribs, spine, and 
sternum form a cage of 
bones for the protection of 
the heart and lungs. This 
part of the body is called 
the chest, or thorax. 

The clavicles and the 
scapulas.— A clavicle, or 
collar-bone, can easily be 
felt on each side of the 
upper part of the front 
of the chest. It extends 
from the sternum to the 
shoulder and forms a brace that keeps the shoulder back. 

A scapula, or shoulder-blade, can be felt on each side at the 
upper part of the back. Each scapula is a strong, irregularly 
shaped bone, and is connected by joints with the long bone of 
the upper arm and with the clavicle of the same side. 

The arms and the hands. — In the upper arm there is a long 
bone called the humerus. It extends from the shoulder to the 
elbow. In the forearm there are two bones of nearly equal 
size, the radius and the ulna, which extend from the elbow 




THE RIBS AND BREAST BONE 



THE HONKS 



183 



(See the picture on 




to the wrist. 
page 178.) 

There are eight short bones, 
called the carpal bones, in the 
wrist, and five long bones, called 
the metacarpal bones, in the palm 
of the hand. As you can see by 
the picture, there are fourteen 
bones in the fingers. They are 
called phalanges. 

The legs and the feet.— The 
longest and largest bone in the 
body is the thigh-bone, called the 

J §> ' BONES OF THE WRIST AND HAND 



femur. The knee-joint is 
protected by a small bone, 
the knee-pan, or patella. 
There is no bone at the 
elbow that corresponds to 
this bone at the knee. 

There are two bones in 
the leg between the knee 
and the ankle. One, the 
tibia, is large and strong; 
the other, the fibula, is small 
and slender. 

There are seven short 




BONES OF ANKLE AND FEET 



184 PHYSIOLOGY FOR YOUNG PEOPLE 

bones, called tarsal bones, in the ankle and instep. The five 
long bones of the foot resemble the five long bones in the 
palm of the hand, and the fourteen bones of the toes are much 
like the fourteen bones of the fingers. 

The big toe, however, differs from the thumb. The bones of 
the big toe lie beside the bones of the other toes and parallel 




THE PELVIS 



with them. The bones of the thumb are not parallel with the 
bones of the fingers, but are so arranged as to allow the thumb 
to be brought opposite the fingers. This arrangement adds 
greatly to the usefulness of the hand by increasing its power to 
grasp and hold things. 

The pelvis. — Two irregularly shaped heavy bones form the 
hip bones. Together with the sacrum they make the pelvis, a 
bony basin that supports the abdomen. 

Color of bone. — A bone in a living animal is pinkish- white 



THE BONKS 



L85 



in color. This color is due to the presence of blood in the tiny 
blood tubes of the bone. After a bone has been cooked, or 
exposed for a time to the weather, its blood disappears, and 
the bone loses its reddish color and becomes 
white. 

Composition of bone. — Bone is composed 
of animal matter and mineral matter closely 
blended. The mineral part of a small bone 
may be removed by soaking it for three or 
four days in a pint of water to which two 
ounces of muriatic acid have been added. 
When the bone is taken out, only the animal 
part is left. This animal part is so soft and 
flexible that if the bone is a long one, such as 
the leg of a chicken, it may easily be tied 
into a knot. 

On the other hand, the animal part of a 
bone may be removed by fire. If a bone is 
placed in a hot fire for two or three hours 
the animal matter may be entirely consumed and only the min- 
eral matter will remain. 

The animal matter of bone resembles cartilage. It makes the 
bones tough and elastic ; it forms about one-third of the bone in 
grown people. The mineral matter makes the bones hard and 
strong. It forms about two-thirds of the bone in grown people. 

Structure of bone. — The outer part of all bones is smooth 
and hard. It is composed of dense, compact tissue. The inner 




A CHICKENS LEG- 
BONE TIED INTO 
A KNOT 



186 



PHYSIOLOGY FOR YOUNG PEOPLE 




part of all bones, except the shaft of a long one, is made up of 
tissue that is loose and spongy. 

If a long bone that has been well dried is divided lengthwise, 
as is shown in the picture, it is seen that 
the ends are not hollow but composed of 
spongy tissue covered with a thin layer 
of dense, compact tissue. The shaft 
forms a hollow cylinder, the walls of 
which are composed of dense, compact 
tissue. 

The hollow cylindrical shape of these 
long bones gives them both strength and 
lightness. The advantage of this shape 
for strength may be shown in this way: 
Take two similar sheets of paper. Roll 
one into a hollow cylinder and fold the 
other so that the folds will lie upon one 
another. Now support these pieces of 
paper at their ends, and suspend a weight 
from the middle of each. You will find 
that the cylindrical paper will sustain 
a much heavier weight than the paper 
that is folded. 

On examination with a microscope the compact parts of 
bone are seen to resemble the spongy parts in structure. But 
in the compact parts the solid matter is packed more closely 
together and the spaces between its particles are much smaller. 



A LONG BOXE 



THE HONKS 



in; 




BOXE HIGHLY MAGNIFIED, SHOWING 
STRUCTURE 



This picture shows the appearance of hone when highly mag- 
nified. The large spots represent channels in the bone for 
blood tubes. These channels are called the Haversian canals. 
The smaller dark spots arranged around them in circles repre- 
sent cavities in which the 
bone cells are contained. 
These cavities communi- 
cate with each other by 
means of minute canals, 
which are shown as fine 
dark lines running out from 
the spaces in all directions. 
Part of the blood oozes 
through the walls of the 
blood tubes, flows out from the Haversian canals and feeds 
the bone cells. In early life the bone cells take from the blood 
mineral matter which they deposit around themselves as inter- 
cell liar material. It is largely composed of lime and makes 
the bones hard and firm. 

Marrow. — The central canal in the shaft of long bones con- 
tains a yellow, pulpy substance called marrow. It consists 
chiefly of fat and blood tubes. In the spaces of spongy bone 
there is also a kind of marrow, which is reddish in color. 

Periosteum. — Closely adhering to the surface of all bones is 
a thin sheet or membrane, called the periosteum. It is com- 
posed of connective tissue, arteries, and veins. From these 
arteries in the periosteum branches pass through small holes 



188 PHYSIOLOGY FOR YOUNG PEOPLE 

into the interior of the bone. Here they divide into smaller 
branches, which extend along the Haversian canals in the bones. 
The small holes for these arteries can easily be seen by ex- 
amining the surface of a dry bone. 

The long bones increase in length by successive deposits of 
bony material added to their ends. Increase in thickness is 




THE PERIOSTEUM 

caused by deposits beneath the periosteum, like successive rings 
formed under the bark of a growing tree. 

The joints. — The bones of the skeleton are fastened together 
by means of joints. Some joints, like those of the hip and the 
shoulder, allow very great freedom of movement. Others, like 
those of the spine, allow slight movements, while at the joints 
of the skull the bones are fixed and cannot move. 

You know that doors work on hinges. The knee and elbow 
are both good examples of hinge joints. The upper end of the 
humerus and the upper end of the femur are round, like a ball. 
The ball of the humerus fits into a cup-shaped depression, or 
socket, in the scapula at the shoulder, and the ball of the femur 
fits into a socket in the hip-bone. The joints at the hip and 
shoulder are therefore called ball-and-socket joints. 



THE BONES 



189 



The ends of the bones in the more movable joints are covered 
with cartilage in order to keep them from rubbing against one 

another as thev move. 

«/ 

Disease of the joints is most prevalent in childhood and early 
life. A common form of joint disease is caused by tuberculosis. 
It occurs frequently at the hip, and 
is known as hip-joint disease. The 
best means for preventing such dis- 
eases include an abundant supply of 
wholesome food, avoidance of alcohol 
or tobacco, daily exercise in the open 
air, and sanitary dwellings, into which 
the sunshine is allowed to enter freely. 

The ligaments. — Bones are held 
together at the joints by short, tough, 
white, glistening bands of connective 
tissue, called ligaments. These are 
soft and flexible and allow great free- 
dom of movement, yet are strong and tough and hold the bones 
securely in their proper places. In the picture you can see how 
the bones of the wrist are firmly held together by ligaments. 

The inner surfaces of the ligaments of movable joints are 
lined with a smooth membrane that secretes an oily fluid, called 
synovia, from its resemblance to the white of egg. Synovia is 
sometimes called joint-oil, as it prevents friction in the joint of 
the body in much the same way that oil prevents friction in the 
joints of a machine. 




LIGAMENTS OF WRIST 
AND HAND 



190 PHYSIOLOGY FOR YOUNG PEOPLE 

Sprains. — Two of the most common injuries to joints are 
sprains and dislocations. A sprain is caused by the forcible 
stretching and twisting of a joint. This injury occurs most 
frequently in the wrist and ankle. A sprain of the wrist usually 
results from a fall on the hand, and a sprain of the ankle is 
usually caused by a misstep or a fall upon the foot. The injury 
may be very slight, and recovery may take place in a day or two; 
or the injury may be very severe, and recovery may be slow 
and tedious. A bad sprain is often worse than a fracture of the 
bone; not because the injury is really more severe, but because 
sprains are so often neglected. In slight sprains the pain may 
be quickly relieved by cold applications. All severe sprains 
should be treated by a doctor. 

Dislocations. — The ends of bones that form a joint are 
sometimes displaced. When the joint surfaces are entirely 
separated from each other the dislocation is said to be com- 
plete. When the joint surfaces are still partially in contact, 
though displaced from their usual positions, the dislocation is 
incomplete. The ligaments that hold the bones in place are 
stretched and torn. As soon as possible the aid of a physician 
should be obtained, and the bones should be put back into 
their usual positions. Bones are sometimes dislocated and 
broken at the same time. The swelling, bruising, and pain 
that are often present may make it difficult, or impossible, to 
determine at once whether the bones are also fractured or not. 
In such cases the X-rays are very helpful. If the dislocation is 
simple, and the bones are put back with little delay, the injury 



THE HONKS 19] 

is usually soon repaired, although the joint may be somewhat 
stiff and weak for a while. 

Broken bones. — A bone may be broken as the result of a 
fall or other accident. Pain is usually felt at the point where 
the break occurs, and some swelling of the parts usually appears 
within a few hours. When a bone is broken, the periosteum, 
blood tubes, and nerves at the place where the fracture has 
occurred are injured. Blood trickles out between the frag- 
ments under the flesh and the skin. This blood is absorbed 
in a short time and takes no part in the healing process. 

When the bone is set and the healing begins, the cells of the 
periosteum and marrow divide and thus increase in number, 
forming a soft mass around and between the broken ends. 
Lime salts are then deposited by the cells, and the soft mass 
gradually becomes hard and firm. The broken ends are in 
time securely united by the formation of new bone around and 
between the broken fragments. This new bone that unites the 
fragments is called the callus. It usually forms a hard swelling 
and may be felt at the site of the fracture for a long time after 
union is complete. 

In young people a broken bone will unite in two or three 
weeks, but in grown persons the time required may be from four 
to six weeks, or even longer. Even after firm union of the broken 
ends has taken place, the parts remain weak for a time. 

Care of the bones. — The bones of young persons are liable 
to grow out of shape if pressure is applied to them too con- 
stantly. Improper positions in standing, walking, or sitting, if 



192 PHYSIOLOGY FOR YOUNG PEOPLE 

continued, may lead to deformity. Constant stooping or bend- 
ing to one side may in time cause one to be round-shouldered, 
flat-chested, or may give rise to curvature of the spine. Any 
habitual one-sided position, if persisted in, may give rise to a 
deformity which may become permanent. 

Bone deformities seldom occur in strong, vigorous, well-fed, 
ambitious children, but are most frequent in those that are pale 
and delicate and have weak muscles. 

Such deformities are rare, too, in persons that are compelled 
to maintain an erect position. Soldiers, and those that are 
accustomed to carry weights, such as baskets of fruit or buckets 
of water, on their heads do not develop deformities, simply be- 
cause they are obliged to hold the body erect. Many deformi- 
ties are due to want of life enough to sit up or stand up straight. 
They are consequently most frequent in careless, lifeless per- 
sons, who are in the habit of sitting much of the time with their 
backs twisted, or bent to one side in a half-curved position. 

How to prevent deformity. — Good food, regular meals, 
sufficient sleep, healthful surroundings, and suitable exercise 
in the open air are of the greatest importance. They tend to 
harden the bones, develop the muscles, and give the strength 
that is necessary to maintain the body in a proper posture. 

Children should form the habit of holding the body erect. 
While standing, the weight of the body should be firmly sup- 
ported by both feet. In walking, the chest should be kept 
up and the head erect. It is true that by sitting or standing 
too long in one position certain muscles become tired, and that 



THE HONKS 193 

to relieve them frequent change of position is necessary; but 
care should be taken to avoid stooping, or bending habitually 
to one side. 

All clothing should be loose and comfortable. Shoes should 
not be too narrow, or have heels that are too high, for the bones 
of the feet may be forced out of place by such shoes. If the 
clothing about the waist is too tight the ribs may be pressed 
inward, and the organs in the thorax and in the abdomen may 
be pushed out of place and hindered in their work. 

It is a false notion that tightly fitting garments give support 
and additional strength. They may appear to do so for a time, 
but it is a law of nature that constant artificial support to any 
part hinders development and is a cause of weakness. The 
chest and waist should never be constricted by clothing. 

SUMMARY 

1. Bones form the framework or skeleton of the body. The skeleton 
supports the soft tissues, protects them, and gives shape to the body. 

2. The spinal column is the central structure of the skeleton. 

3. This column has a hollow space for the spinal cord. 

4. The spinal cord extends downward from the brain, through a hole 
in the base of the skull, into the spinal column. 

5. The bones of the cranium are joined by irregular edges called sutures. 

6. The ribs, spine, and sternum protect the heart and lungs. 

7. The bones of the arm and hand resemble those of the leg and foot. 

8. The pelvis rests upon the legs and supports the trunk. 

9. Bone is made up of animal matter and mineral matter. 

10. The outer part of bone is hard and compact. The inner part of 
short bones is spongy. 

11. The shape of long bones makes them light and strong. 



194 PHYSIOLOGY FOR YOUNG PEOPLE 

12. The Haversian canals in bones are channels for blood tubes. 

13. Minute cavities containing bone cells are arranged around the 
Haversian canals. These cavities are connected by very small canals. 

14. A thin membrane, called the periosteum, adheres to the surface of 
all bones. 

15. The joints at the shoulder and hip are ball-and-socket joints. 

16. The joints at the elbow and knee are hinge joints. 

17. Bones are held together at the joints by ligaments. 

18. The inner surface of a ligament of a movable joint is lined with a 
membrane that secretes an oily fluid. 

19. A broken bone may be set, i.e., the ends put together in their right 
position. 

20. Bones may be bent out of shape by tight clothing or improper posi- 
tions. 



CHAPTER XIV 
THE MUSCLES 

How muscles produce movement.— Muscles have the 
power to contract, which makes them shorter; and to relax, 
which makes them longer. It is this power of contracting and 
relaxing that enables muscles to produce movement. They not 
only move themselves, but they cause bones to which they are 
fastened to move. The biceps, a muscle of the arm, is attached 
at its lower end to a bone of the forearm. When this muscle 
contracts it pulls on the bone of the forearm and the hand 
and forearm are drawn upward. In a similar way other 
muscles are fastened to the sides and back of the arm. When 
these contract they move the arm in other directions. 

When the muscles on the right side of the neck contract the 
head is turned to the right, and when those on the left side con- 
tract the head is turned to the left (see page 197). 

As we chew our food, muscles attached to the lower jaw con- 
tract and draw it downward, others contract and draw it up 
again. 

Muscles of the legs, by contracting and relaxing, enable 
us to walk, run, and jump. 

The tendons. — The tendons are white, glistening cords that 

connect muscle to bone or other part of the body. Some 

tendons are round, others are flattened. 

195 



196 



PHYSIOLOGY FOR YOUNG PEOPLE 




In this picture the tendons of the muscles of the forearm 
are shown, and also their attachment to the bones of the 
fingers. When we move the fingers rapidly we can see the 
tendons that belong to the muscles of the back of the arm 

moving under the 
skin. 

How our muscles 
are made to move. 
— We have below 

MUSCLES OF FOREARM AND THEIR TENDONS 

on the left the pict- 
ure of a muscle such as can be found in the leg of a frog. 
If this were a properly prepared muscle, about two inches long, 

instead of a picture, and 

we were to pinch it or 

prick it with a pin, it 

would shorten and become 

an inch and three-quart- 
ers, or perhaps only an 

inch and a half in length. 

It would then resemble 

the muscle on the right. 

Whenever we pinch or 

prick a muscle in this 
way, we are said to stimulate it. The stimulation makes 
the muscle contract and become shorter. We can stimulate 
a muscle and make it contract without touching it. A 
little nerve ends in each muscle. See the outline of a 





LEG MUSCLE OF 
A FROG 



LEG MUSCLE OF 
A FROG WITH 
ITS NERVE 



THE MUSCLES 



197 



muscle with its nerve on page 196. If such a nerve is 
pinched or pricked the muscle will contract, although the 
muscle itself is not touched at all. When we pinch or 




MUSCLES OF NECK AND HEAD 



prick the nerve, we stimulate it, and thus start a message, or 
nerve impulse as it is called, that travels along the nerve and 
stimulates the muscle. When the nerve impulse reaches the 
muscle, the muscle contracts. Contraction of muscle in the 



198 



PHYSIOLOGY FOR YOUNG PEOPLE 



living body is caused in a similar way. Whenever you decide 
to close your hand, muscles lying along the front of the 
arm contract and draw the fingers down. 
When you determine to open the hand 
again, muscles lying along the back of 
the arm contract and pull the fingers up. 
A simple act of the will starts a nerve impulse 
that travels from the brain along a nerve, or 
nerves, to the proper muscles. On the ar- 
rival of this nerve impulse at the muscles, 
a contraction quickly follows. After a mus- 
cle has contracted, it returns sooner or later 
to its original length and shape, that is, it 
relaxes. 

When a muscle contracts and relaxes seve- 
ral times in rapid succession it becomes 
fatigued. Its power to contract is dimin- 
ished, or may be entirely lost. This power 
is regained, however, after a period of rest. 

Voluntary muscles.— The muscles that 
are attached to the bones of the skeleton are 
often called skeletal muscles. They are the 
muscles by which we move a part of the 
body or move from place to place. For the most part 
they are arranged in pairs; for instance, one muscle, the 
biceps, pulls the arm up; its mate, the triceps, pulls the 
arm down. As one of the pair shortens, the other lengthens. 



UNCONTRACTED 
BICEPS OF 
UPPER ARM 



THE MUSCLES 



L99 



We can cause the skeletal muscles to contract whenever 

we wish; they are under the control of the will. For this reason 
they are also called volun- 



tary muscles. 

There are some voluntary 
muscles, as, for instance, the 
one around the mouth, that 
are not skeletal, since they 
are not fastened to any bone. 



*m*«HiM«ia..,i,.>,..«. «.,„„„„„, 



H*MH««Hlflll«n ((l „ Mf , |if 



**m 



u 



THREE FIBRES OF VOLUNTARY MUSCLE 
(Magnified) 



Structure of voluntary muscle.— A 

voluntary muscle is made up of a large 
number of small cells, called fibres, bound 
together into bundles by connective tissue 
and minute blood tubes. It is from the 
blood in these tubes that the muscles 
obtain the nourishment that makes them 
grow and gives them the power to con- 
tract. 

This is a highly magnified picture of 
part of a voluntary muscle fibre, with the 
end of a nerve attached to it. You can 
see fine lines or stripes that cross the fibre 
from side to side. On account of these, 
voluntary muscle is sometimes called 
striped muscle. When lean meat is boiled, the connective 
tissue is softened so that the bundles of muscle fibres fall apart 
or may be easily separated. 




VOLUNTARY MUSCLE 
FIBRE WITH NERVE 
ENDING 

(Highly magnified) 

1. Muscle fibre. 

2. Ending of nerve. 
From "Gray's Anatomy" 



200 



PHYSIOLOGY FOR YOUNG PEOPLE 



Involuntary muscle. — Many internal organs, such as the 
stomach, the intestine, the arteries, and the veins, contain 
muscles in their walls. These muscles contract at the proper 
time, whether we wish them to do so or not. They are not 
under the control of the will. For this reason they are called 

involuntary muscles. When the 
involuntary muscles in the walls 
of the stomach and intestine 
contract, the food in these or- 
gans is moved along and is 
mixed with the digestive juices. 
When the involuntary muscles 
in the blood tubes contract, 
they assist in pushing the blood 
along in its course through 
the body. 

Structure of involuntary 
muscle. — Involuntary muscle 
consists of cells cemented to- 
gether along their edges so as to form sheets and bands. This 
picture shows cells of involuntary muscle separated from each 
other and magnified. You can see that these cells are not 
striped like voluntary muscles; hence involuntary muscles are 
sometimes called unstriped muscles. These muscles are also 
richly supplied with blood tubes. 

The heart consists of a large mass of connected muscles. 
Heart muscle differs from other muscle. Its fibres are striped 




CELLS OF INVOLUNTARY MUSCLE 
(Magnified) 



THE MUSCLES 201 

like those of voluntary muscle, but the heart beats whether we 
wish it to do so or not. Its action is not under the control of 
the will. In this respect heart muscle resembles involuntary 
muscle. 

Shape of muscles. — Muscles have many different shapes. 
Some are small, thin, and round; others are short and broad; 
while others are spread out like a fan. The shape of each 
muscle is adapted to the work that it has to do. 

Uses of muscles. — One of the most important uses of mus- 
cles is, of course, to produce movement. 

Another important use of muscles is to help produce bodily 
heat. On a cold day we swing our arms, and walk about or 
run, in order to warm ourselves. If we play or work hard on 
a warm day we become so warm that we perspire freely. The 
increased activity of the muscles causes more food to be oxidized 
in the muscle cells, and this increase of oxidation makes more 
heat in the body. It has been shown by actual experi- 
ment w r ith a thermometer that blood is warmer after it 
leaves a contracting muscle than it was before it entered the 
muscle. 

Still another use of the voluntary muscles is to cover the bones 
and, together w T ith fat, give to the body its rounded form and 
graceful outline. They help also to enclose such cavities as the 
mouth and abdomen and protect the large arteries and nerves 
that lie beneath them. 

Effects of alcohol on muscle. — Some people have the mis- 
taken idea that by drinking alcoholic liquor they are able to <L 



202 



PHYSIOLOGY FOR YOUNG PEOPLE 



an increased amount of work. But it has been proved by many 
careful experiments that such is not the case. 

This is a picture of an instrument that is often used in mak- 
ing such experiments. A string fastened to the second finger 




EXPERIMENT TO SHOW EFFECT OF ALCOHOL 
ON THE MUSCLES 



is passed over a pulley and attached to a weight. The first and 
third fingers are placed in tubes to keep them from interfering 
with the second finger. In this experiment the muscles of the 
second finger are contracted and relaxed every few seconds, the 
weight being raised and lowered each time. This is continued 
until the finger is completely exhausted, and a record is kept of 
the number of times the weight was lifted. 

In order to ascertain the influence of alcohol the experiment 
is tried on the same person at different times; at some of these 
times he drinks a small amount of alcoholic liquor, at other 
times he does not drink any. It has been found, as a result of 
these experiments, that alcohol at first gives increased power to 



THE MUSCLES 203 

work for a short time. But very soon the power to work is 
greatly diminished, so that the total amount of work done with 
alcohol is less than that done without it. 

These results are confirmed by the experience of army officers, 
employers of labor, athletes, and explorers; for they find that the 
body is in better condition for prolonged severe work when 
alcohol is not taken. In this connection, Count von Haeseler, 
Commander of the Sixteenth Army Corps in Germany, says: 
"The soldier who abstains altogether is the best man. He can 
accomplish more, can march better, and is a better soldier than 
the man who drinks even moderately. Mentally and physically 
he is better. -Brandy is the worst poison. Next to it comes 
beer. For a soldier, water, coffee, and, above all, tea, are the 
best drinks." 

Sir John Ross, commander of an expedition to the Arctic, 
says: "The most irresistible proof of the value of abstinence was 
when we abandoned our ship and were obliged to leave behind 
us all our wines and spirits. It was remarkable to observe how 
much stronger and more able men were to do their work when 
they had nothing but water to drink." 

Surgeon-Major Reid, of the Coldstream Guards of the British 
army, says, in his report on the Suakim campaign in Af rica : 
"No spirituous liquors have been used during this campaign. 
I am of the opinion that their absence has largely contributed 
to the efficiency of the troops during the arduous duties per- 
formed by them." 

Those who drink beer and w 7 ine often become fat. The 



204 PHYSIOLOGY FOR YOUNG PEOPLE 

alcohol is more readily oxidized in the cells of the tissues than 
the fat contained in the food. As part, at least, of this fat is 
not needed, it is stored up in different parts of the body. Some 
is stored in the connective tissue between the muscle fibres and 
interferes with the work of the muscles. 

The following statement is quoted from an article on athletes 
in the New York Herald of March 14, 1909, by Mr. Michael 
C. Murphy, Coach of the track team of the University "of 
Pennsylvania, and of the American Olympic team of 1908. 

"Before concluding this article I want to sound just two more 
warnings to young athletes. If you want to become champions 
and emulate the examples of the men about whom I have been 
writing, then make sure that you leave alcohol and cigarettes 
alone absolutely. Especially beware of alcoholic stimulants 
while training. The men about whom I have written made their 
world records because they let these things alone, because in the 
main they were temperate and lived clean lives. They depended 
entirely on their good condition for their success. 

"One of the strongest arguments I know of against alcohol, cig- 
arettes, etc., for athletes is that the professionals, who train solely 
for the money they can make out of athletics, invariably leave 
them alone. They know they must win to make a living and that 
they cannot win when they disregard these important rules of 
training. 

"Every drop of drink that an athlete takes means just so much 
more hard work to get into condition. I would also caution young 
athletes to avoid overloading the stomach and to keep scrupu- 
lously 7 clean at all times. The man who breaks records is the man 



THE MUSCLES 205 

who is temperate in all things. He is the man who has reserve 
speed and strength at the end of the contest, which always win for 
him and establish the new records. " 

Ann Arbor, Mich., January 8, 1909. 
Dear Sir: — Your letter of the 4th inst. is received. I am very 
glad to inform you that young men under my care, training for the 
different branches of athletics, are required to abstain from the use 
of alcoholic liquors and tobacco. There is no question in my mind 
that the use of alcoholic liquors and tobacco interferes greatly with 
the development and physical condition of young men. The best 
athletes I have had under my care have been young men who have 
never used alcoholic liquors or tobacco in any form. 

Very truly yours, 

Keene Fitzpatrick, 
Director, Waterman Gymnasium, University of Michigan. 

Chicago, III., July 1, 1907. 

Dear Sir: — It is my firm opinion, based on twenty-two years of 
participation in intercollegiate athletics, either as player or as 
coach, that the best results in physical development are secured 
only by total abstinence from the use of alcoholic liquors, tobacco, 
and other stimulants. My opinion is based on careful observa- 
tion of the athletic work of youths who did and who did not use 
stimulants. Sincerely, 

A. A. Stagg, 

Director, The Bartlett Gymnasium, The University of Chicago. 

Philadelphia, Pa., January 11, 1909. 
Dear Sir: — In reply to your letter of January 4th, I would say 
that all candidates for the foot-ball team abstain from the use of 



206 PHYSIOLOGY FOR YOUNG PEOPLE 

alcoholic liquors and tobacco during the season. This is a cast- 
iron rule, which we never allow to be broken. 

Yours very truly, 

William W. Roper, 
Foot-ball Coach, Princeton University, 

SUMMARY 

1. Muscles have the power to contract and relax. This power enables 
them to produce movement. 

2. Many muscles are connected to bone by tendons. 

3. Whatever causes a muscle to contract is said to stimulate it. 

4. Nerves end in muscles, and the usual stimulus is a nerve impulse. 

5. Voluntary muscles are under the control of the will. 

6. They are generally arranged in pairs, one of which becomes longer as 
the other becomes shorter. 

7. Involuntary muscles are not under the control of the will. 

8. Heart muscle differs from other muscle. In appearance its fibres look 
like voluntary muscle, but their action is involuntary. 

9. A large amount of body heat is produced in the muscles. 

10. Muscles help to give the body its shape, to enclose cavities, and to 
protect arteries and nerves. 

11. The use of alcoholic liquor and tobacco weakens the muscles. 



CHAPTER XV 
PHYSICAL EXERCISE 

All organs of the body need exercise. — The natural and 
reasonable use of an organ, such as the arm, does not wear it 
out, but causes the arm to grow in size and increase in strength. 
The right arm, as a rule, measures from a quarter to a half 
inch more around than the left. This difference is entirely due 
tc the fact that the muscles of the right arm are used more than 
the muscles of the left. When muscles are used they increase 
in size and strength, but when they are not used they decrease 
in size and become weak. 

As with the arm, so with all the other organs. The work 
that they do does not wear them out, but gives them increased 
power and health. 

How exercise affects the muscles. — The function of mus- 
cle is to contract and relax. As a muscle contracts, the small 
arteries in it dilate and hold more blood, both at the moment 
of contraction and for some time afterward. A larger amount of 
food and oxygen comes to the cells of the muscles in the larger 
supply of blood. The effect of contraction is to stimulate the 
cells to take in this food more freely and thus build themselves 
up. In this way both the size and the number of muscle cells 
are increased by exercise. 

How exercise affects the lungs, heart, skin, and nerves. 

— The effect of exercise is not confined to the muscles them- 

207 



208 PHYSIOLOGY FOR YOUNG PEOPLE 

selves, but extends to all other parts of the body. The muscle 
cells when exercised consume so much of the oxygen and food 
in the body that a greater supply of these substances is needed. 
Breathing becomes deeper and faster in the effort to supply 
an increased amount of oxygen, and thelungs and the muscles 
that are concerned in respiration are benefited by the increased 
activity. The greater demand for food gives rise to a feeling 
of hunger, so that as a result of regular exercise a man gradu- 
ally eats more food, just as he breathes more air. 

The increased demand for blood by the muscle cells affects 
the circulation, and the heart is stimulated to greater activity. 
Then as a result of the increased activity its muscle fibres are 
developed, and it becomes stronger. 

The union of an increased amount of food and oxygen in the 
cells increases the amount of heat produced by oxidation. Be- 
cause of the surplus of heat the skin becomes more active. 
The small arteries in the skin dilate, sweat glands work with 
greater vigor, and surplus heat is taken from the body as the 
perspiration is evaporated. 

When muscles are exercised, the brain and nerves that con- 
trol the movements of the muscles become active. A large 
number of the cells of the surface of the brain have the special 
work of sending out impulses to muscles to make them contract. 
In addition to these, cells in other parts of the brain become 
active in other ways. As a result, therefore, of muscular exer- 
cise the brain and nerves, too, are developed while performing 
their own functions, and so become better able to perform them. 



PHYSICAL EXERCISE 209 

Fatigue.— If one or more groups of your muscles are kept 
contracted for some time, or are made to contract often, you 
will feel fatigued. This feeling is due partly to the using up of 
the supply of food and oxygen contained in the muscle cells, and 
partly also to the presence in the cells of waste products, which 
are formed faster than they can be carried away. But fatigue 
is due more largely to the exhaustion of the cells of the brain 
which control the movements of the muscles. This is par- 
ticularly true of those movements that require close attention 
and an effort of the will. 

Amount of exercise. — It is impossible to make any rule for 
the amount of exercise that should be taken, because what is 
best for one person may be too much or too little for another. 
Exercise within proper limits is usually followed by more or 
less fatigue; but if there is not, after a night's rest, a complete 
recovery from the fatigue, it is safe to conclude that the exer- 
cise was too severe. 

Time of exercise. — The best results are obtained when 
exercise is taken each day and at regular hours. The best time 
for exercise is before rather than after meals, but there should 
be an interval of at least half an hour for rest between the 
exercise and the meal. If exercise is taken too soon after a 
meal, so much blood may go to the muscles that there may not 
be enough in the digestive organs to enable them to secrete a 
sufficient amount of digestive juices. 

In the case of those that are not robust, it is better to divide 
up the daily amount of exercise into two or three parts. 



210 PHYSIOLOGY FOR YOUNG PEOPLE 

Kinds of exercise. — Any kind of exercise does all that is 
needed to benefit the different organs of the body if it causes 
the principal groups of large muscles to contract freely, without 
over-fatigue. It may be in the form of out-door games, in the 
form of practice in a gymnasium, or in the form of labor. In 
general, work or games in the open air are better than work or 
exercise in-doors. 

The greatest benefits are obtained from exercises that cause 
contractions of the large muscles of the thighs, back, abdomen, 
and shoulders. Contractions of the smaller muscles, such as 
those of the hands and arms, are necessary for their own im- 
provement, but do not furnish sufficient exercise to improve the 
condition of the different organs of the body. On the other 
hand, when exercise is taken that causes contractions of the 
large groups of muscles, breathing becomes deeper, and all 
the air cells of the lungs are called into action; circulation is 
quickened; digestion and excretion are stimulated; and the 
brain and nerves become more active in the performance of 
their functions. 

If a moderate amount of such exercise is taken every day it 
improves the condition of the different organs of the body. 
They, therefore, become better able to do their work, and the 
body is brought into a state of health. For a body is healthy 
when all its organs are doing their work well. 

Work. — Manual labor in the open air, if not too severe or 
prolonged, is one of the best forms of exercise. The farmer, 
the bricklayer, and others that do out-door work have the 



PHYSICAL EXERCISE 211 

benefit of fresli air and sunshine, and at the same time they 
get also a variety of muscular movements that give exercise to 
the principal groups of muscles. 

It is the custom in factories to use labor-saving machinery. 
In operating much of this machinery there is little variety of 
movement, and exercise is given to only a few groups of mus- 
cles. The operator sits at his machine and feeds material 
to it by a few movements of the arm and the hand. The 
same movements are made over and over again all day long, 
and groups of large muscles do not get the amount of exercise 
they require. 

Compared with this, work on a farm furnishes a much greater 
variety of movements. On a farm a man or a boy can get such 
mixed kinds of exercise as grooming horses, caring for cows 
and other animals, tilling soil, pitching hay or straw, sawing 
and splitting firewood, and pumping water. These require 
body-bending, lifting weights, and walking, so that abundant 
exercise is furnished for all the groups of larger muscles. 

Games. — Play is the natural form of physical exercise for 
children. If they have the chance to play in safety, children 
will take all the exercise they require for normal, healthy de- 
velopment during the early years of life. Their whole time will 
be occupied in eating, sleeping, and playing. 

At seven or eight years of age, boys and girls become inter- 
ested in games in which there is competition. Some of these 
are tag, blackman, prisoner's base, leap-frog, and various ball 
games. By means of the exercise in these and other games, the 



212 PHYSIOLOGY FOR YOUNG PEOPLE 

heart, the lungs, and the muscles are developed and strength- 
ened. Bodily skill is acquired and the mind is trained in 
observation, in judgment, and in the power of choosing and 
applying proper means to get the desired results. A valuable 
feature of games is the interest which they excite. 

After thirteen or fourteen years of age other games of a more 
vigorous nature claim the attention. Skating, hockey, base- 
ball, cricket, tennis, basket-ball, lacrosse, and foot-ball take the 
place of the simpler games. A feature of these games is that 
they are played in teams; the players no longer act separately, 
but unite their efforts for the benefit of their team. These con- 
tests represent the most severe form of exercise in games. 
Through them muscles and the organs of respiration and of 
circulation attain a high degree of development, and the power 
of endurance is acquired. Valuable habits of mind are formed 
by the necessity of close continued attention, quick judgment 
and the nice precision required for prompt muscular action. 

In learning to play these games the brain reaches a high 
state of development through sending out to the muscles the 
impulses that cause the exact movements required. This de- 
velopment gives increased power for prolonged and difficult 
mental effort in after life. 

Exercise in a gymnasium.— A gymnasium has the advan- 
tage of allowing exercise to go on when the weather is unsuited 
to out-door games and sports. It also permits of special exer- 
cise with suitable apparatus to develop any groups of muscles 
that are weak and need special attention. 



PHYSICAL EXERCISE 213 

One form of exercise in a gymnasium consists of drills, either 

with or without apparatus. Such drills should be short and 
not too difficult. A leader should perform the movements, and 
the class shoulcj follow the leader. Drills sometimes consist of 
a long series of movements that are accurately memorized and 
done by silent count without any leader or word of command. 
These drills exhaust the nervous system by making too great 
demand on the memory and the power of attention. 

Whenever it is possible in gymnastic exercises, the spine 
should be kept erect. This position gives the largest capacity 
of chest, and affords the greatest room for free movements of 
lungs and heart. 

Strength is acquired slowly. It is the result of many move- 
ments, not too difficult, done daily for a considerable time. 
Bear in mind that strength cannot be acquired in a short time 
by making a few movements that require great muscular effort. 
Nor should the aim of exercise be the development of one or 
more groups of muscles in order that certain unusual feats of 
strength may be performed. The purpose of exercise should be 
to use all of the principal groups of large muscles, so that the 
body as a whole may be brought into the best state of health. 

SUMMARY 

1. The reasonable exercise of an organ strengthens it. 

2. Exercise brings to a muscle a larger supply of blood, and, therefore, 
a larger supply of food and oxygen. 

3. When the muscles are exercised, there is a greater demand for food. 

4. When the muscles are exercised, breathing becomes deeper and 
faster in order to supply needed oxygen. 



214 PHYSIOLOGY FOR YOUNG PEOPLE 

5. The blood must flow faster to supply food and oxygen to the muscles 
during exercise. Consequently, the heart becomes more active. 

6. As more food is oxidized in the muscles, a greater amount of heat is 
produced. The arteries of the skin dilate, and the sweat glands become 
more active. 

7. Fatigue is due partly to the using up of food and oxygen in the muscle 
cells, and partly to the increase of waste products in these cells. 

8. Exercise is too severe if recovery from fatigue does not follow a night's 
rest. 

9. Exercise should be taken daily, at regular hours, and not immediately 
before or after a meal. 

10. Exercise should produce free contraction of the groups of large 
muscles. 

11. Manual work in the open air is one of the best forms of exercise. 

12. Games are the natural exercise for children. 

13. In drills the class should follow a leader, and should not be required, 
to memorize a long series of movements. 

14. Exercise should consist of easy movements frequently repeated. 
Movements requiring great effort should be avoided. 



PART IV 

THE FUNCTION OF IRRITABILITY AND 
CONTROL 

CHAPTER XVI 

PLANT AND ANIMAL IRRITABILITY AND CONTROL 

When you try on a shoe that is too small for you, the press- 
ure on your foot causes a message to go along nerves from 
your foot to your brain, and when the message reaches the 
brain you know that the pressure hurts your foot. You then 
send out from your brain along nerves messages directing cer- 
tain muscles to raise your foot and other muscles of the hand 
and body to take off the shoe. 

In this illustration we see two functions of our nerves. Press- 
ure on the foot rouses to a state of activity nerves that end in 
its surface, and a message, or impulse as it is more often called, 
is conducted to the brain. These nerves are said to be irri- 
tated by the pressure, and this power of being irritated is called 
irritability. Anything that irritates a nerve and rouses it to 
activity is called a stimulus. When an impulse from the foot 
arrives at the brain, another impulse starts from the brain and 

causes muscles to act. Thus another function of nerves is to 

215 




GRAIN OF CORN GROWING IN 
HORIZONTAL POSITION 



216 PHYSIOLOGY FOR YOUNG PEOPLE 

control the action of the muscles and other organs of the body. 
While nerves are the special organs of irritability, other tissues 
are to some extent irritable, and respond to stimuli. 

Plant irritability.— You remember that the active part in a 
living cell is the protoplasm. Now, living protoplasm, wherever 

found, shows some irritabil- 
ity, but it is not all equally 
irritable. The protoplasm of 
a living nerve-cell, for in- 
stance, is much more irritable 
than the protoplasm of a 
living muscle cell, or vegeta- 
ble cell. Though irritability 
is most noticeable in animals that have a well developed 
nervous system, yet it is a property of all living things, and in 
plants there are many interesting and wonderful instances of it. 
Irritability serves a useful purpose both in the plant and the 
animal. If, for example, water that the plant or animal needs 
is near it, the water acts as a stimulus, and the plant or animal 
makes an attempt to get to it. If, on the other hand, there is 
near by something that would hurt, it acts as a stimulus, and 
the plant or animal makes an attempt to avoid it. 

Since the plant derives its food material from the soil and the 
air, it receives stimuli chiefly through its leaves and the tips of 
its roots. 

Irritability of roots, leaves, and stems.— If a kernel of 
corn or other seed is planted in moist sawdust, and, after it 



PLANT AND ANIMAL IRRITABILITY 



217 



begins to grow, is placed in a horizontal position and still kept 
moist, the end of the root will, within a day or two, turn down- 
ward toward the centre of the earth, and the end of the stem will 
turn upward away from the centre of the earth. The stimulus 
in these movements is gravity, the force which 
causes a ball that is thrown up to return to the 
earth. In a similar way, the end of a growing 
root will bend to pass a stone or other solid, to 
reach moisture, or to enter more fertile soil. 

Another illustration of root irritability is seen 
in its response to the stimulus of heat. Roots 
will grow toward hot water or steam pipes in 
the soil, but will not come into contact with 
them. When the soil near the pipes attains a 
certain temperature the end of the root will 
cease growing toward the heat and will bend 
away from it. Experiments have shown that 
roots of Indian corn will grow toward heat 
until the temperature is 99.5° F., when they 
will bend and grow away from soil that is warmer. A writer 
on this subject says that the sensitiveness to heat that causes 
a man who is cold to approach the fire, but not to draw. too 
close, and, when warmed, to move to a slightly cooler spot, 
is not peculiar to him or to other higher animals. This 
response to heat illustrates the habit of all living things that 
can move to seek positions that best promote their well-being. 1 
^ee Peirce's Plant Physiology, p. 221. 




GRAIN OF CORN 
GROWING IN 
UPRIGHT POSI- 
TION 



218 



PHYSIOLOGY FOR YOUNG PEOPLE 



Leaves are very sensitive to light. The leaves of green plants 
need the aid of sunlight in the manufacture of food from the 
materials that the plant takes from the soil and the air. 

When light falls more on one side of a plant than on the other 
side we have a common illustration of irritability. In response 

to this stimulus the plant 
slowly bends toward the 
light, so that it may fall 
equally on both sides. 

Plants usually expose 
the broad upper surfaces 
of their leaves to the 
light, but there are 
plants, such as the com- 
mon bean, and oxalis, 
that turn the broad sur- 
face of their leaves away from the light and expose an edge to 
it when the light becomes too strong for them. 

Many plants are sensitive to touch. Climbing plants, such 
as the hop, vine, and ivy, have stems which are not strong 
enough to hold the plant up so that its leaves may do their 
work freely in the open air and sunlight. When the stem of 
the hop or morning-glory comes in contact with a string or a pole, 
the stem responds to the stimulus of contact and closely twines 
for support around the object touched. 

The stem of the grape-vine is not strong enough to support 
itself, but it produces tendrils. When a tendril of a grape-vine 




TENDRILS OF VIRGINIA CREEPER BEFORE 
CONTACT 



PLANT AND ANIMAL IRRITABILITY 



210 



touches anything that it can twine around, it slowly coils around 
the object, and thus affords support to the weak stem. 

The Boston ivy and Virginia creeper are climbing plants that 
have tendrils. These tendrils do not coil around objects, but 
when the end of the tendril comes in contact with a wall or 
other support it secretes a sticky fluid that holds the. stem fast 
to the wall. 

Perhaps the most remarkable instances of plant irritability 
are seen in the movements which are made by the leaves of 
Venus's fly-trap and the sundew when they capture insects for 
food. On the outer end of the leaf of Venus's fly-trap there are 
three short spines that 
are sensitive to contact. 
When an insect touches 
one of these spines the 
leaf closes quickly. 
Numerous glands on the 
surface of the leaf then 
secrete and pour out on 
the captured insect a fluid 
that digests its nutritious 
parts. (See page 221.) 

The upper surface of 
the leaf of the sundew is furnished with many short stalks. On 
the end of each stalk is a little round gland that secretes a 
sticky fluid and is sensitive to contact. When an insect alights 
on these glands it becomes entangled in the sticky secretion and 




TENDRILS OF VIRGINIA CREEPER AFTER 
CONTACT 



220 



PHYSIOLOGY FOR YOUNG PEOPLE 




LEAF OF SUNDEW CLOSING ON 
CAPTURED INSECT 



soon dies, because the fluid 
closes up the air tubes of the in- 
sect and it cannot breathe. The 
other stalks bend slowly and 
bring their sticky glands down 
upon the insect, and then the 
glands secrete and pour out on 
the insect a fluid that digests its 
nutritious parts. 

Plants usually obtain from 
the soil, through their roots, the 
nitrogen that they need for the growth and repair of tissue. 
But plants like these grow on moss in marshes and 
cannot get enough nitrogen through their roots, and so they 
obtain it through their leaves from the bodies of insects. 
Animal irritability and control.— In animals that consist 
of one cell, such as the amoeba, 
there are no nerves. Irritability 
is due to the protoplasm of the 
single cell. Recent experiments 
have been conducted in order 
to find out in what ways these 
microscopic animals are irrita- 
ble, and it has been shown that 
they respond to many kinds of 
stimuli. Among these are con- 
tact, heat, and cold. 



W^'M 



m 




LEAF OF SUNDEW OPEN 



PLANT AND ANIMAL IRRITABILITY 



221 




END OF LEAF OF VENUS S FLY-TRAP 



It is possible to draw out a 
heated glass rod into such a 
fine thread that its end is 
smaller than one of these mi- 
nute animals ; and when the end 
of such a glass thread is, with 
the aid of a microscope, drawn 
along the side of the animal, 
it will move away from the irritating contact. If a number of 
these animals are placed in w T ater contained in a small vessel 
which is then heated at one end, they will move away to the 

other end. If one end is 
cooled, they will move to 
the warmer end. If one 
end is heated and the 
other cooled, they will 
move from both ends 
and stay in the middle. 
As we ascend the 
scale of animal life, one 
of the first animals in 
which nerves have been 
found is the jelly-fish. 
This animal has an 
umbrella-shaped body, 
as shown in the picture, and on the lower side of the umbrella 
is a thin layer of muscle tissue. The animal moves by 




A JELLY-FISH 



222 



PHYSIOLOGY FOR YOUNG PEOPLE 



NETWORK OF NERVE TISSUE IN 

JELLY-FISH 

(Highly magnified) 



partly closing and opening its 
umbrella while leaning to one 
side. As the umbrella closes it 
presses against the water within 
it and thus forces the animal 
backward. The layer of muscle 
tissue by which these movements 
are made is overspread with a 
very fine network of nerve tissue, 
and this nerve tissue regulates the 
contraction of the muscles. It is 
noteworthy that in this early ap- 
pearance of different kinds of tissue in the scale of animal life one 

kind is muscle tissue, and the other is nerve tissue whose work 

is to control the work of the muscle tissue. 
Nerve tissue.— Nerve tissue, like other 

tissue, is made up of cells. These cells 

vary greatly in size and shape, but each 

nerve cell is composed of two parts: one 

is an enlarged part containing a nucleus, 

which is called a nerve-cell; the other part 

consists of one or more projections from 

the nerve-cell. 1 A long projection is called 

a nerve-fibre. What we commonly call 




NERVOUS SYSTEM 
OF A BEE 



1 Observe carefully that nerve cell, without a hyphen, is used as the 
name of the entire cell; and that nerve-cell, with a hyphen, is used as 
the name of part of the cell. 



PLANT AND ANIMAL [MUTABILITY 



223 



nerves are nerve- 
fibres bound togeth- 
er. They are always 
projections from 
nerve-cells. Nerve- 
cells can both start 
and receive impulses. 
Nerve-fibres merely 
conduct impulses, 
some conduct im- 








A. — NERVE CELL ENDING IN 
ANOTHER NERVE CELL 

B. NERVE CELL ENDING IN 

MUSCLE 

1. Nerve cell containing nucleus. 

2. Nerve-fibre. 3. Endings 

of nerve-fibre. 



NERVOUS SYSTEM OF A MUSSEL 

1. Ganglion of esophagus. 2. Ganglion of foot. 3. Gang- 
lion of organs of digestion. (F) Foot. 



pulses from nerve-cells and others 
conduct impulses to nerve-cells. 
In these pictures, nerve-cell A 
connects with another nerve-cell; 
nerve-cell B ends in muscle. 

As we ascend the scale of life, 
animals become more active, and 
therefore require more muscle 
cells to produce movements, and 
more gland cells to furnish secre- 
tions with which to digest a 
larger amount of food. Conse- 
quently, muscle cells are massed 
together in very large numbers 
to form a muscle, gland cells are 
massed together in glands, and 
nerve cells are massed together 



224 PHYSIOLOGY FOR YOUNG PEOPLE 

in order to control the cells of the muscles and the glands. A 
mass, or group, of nerve cells working together, is called a 
ganglion or nerve centre. 

A simple kind of nervous system.— One of the simplest 
arrangements of nerve ganglions is seen in such animals as the 
oyster and the mussel. In these animals the nervous system 




SECTION OF FOREPART OF EARTHWORM, SHOWING ALIMENT- 
ARY CANAL, BLOOD TUBES, AND NERVES 

1. Mouth. 2. Nerve-ring. 3. Alimentary canal. 4. Row of gang- 
lions. 5. Blood tubes. 

consists of ganglions placed wherever an important function is 
located, and the ganglions are connected by nerve-fibres. A 
good illustration of this simple arrangement is seen in the 
common mussel of rivers and smaller streams. Two connected 
ganglions are placed either above, or on each side of, the esoph- 
agus. These send nerve-fibres to the sensitive region about the 
mouth. Below the esophagus are other ganglions, which send 
out nerve-fibres to the foot with which the animal burrows. 
Farther back in the body are other ganglions which send out 
nerve-fibres to the organs of digestion (see page 223). 

A higher kind of nervous system.— A more complex ner- 
vous system is found in such invertebrate animals as the earth- 
worm, insects, and the lobster. The bodies of such animals 




PLANT AND ANIMAL IRRITABILITY 225 

are made up of a succession of parts. Each pari is called a 

segment. Then 4 is a ganglion above and another below the 
esophagus. These, with their connecting nerve-fibres, form a 
nerve-ring, or collar, 
around the esophagus. 
The ganglion above 
the esophagus, in the 
nerve-ring, sends off 
nerve-fibres to such 
sense organs as the 
eyes and the feelers in l> 
those animals that F 
have these organs. SHELL 0F MUSSEL WITH F00T PROTRUDING 

& (F) Foot 

It is also the seat of 

whatever instinct or intelligence the animal possesses. The 
ganglion below the esophagus sends out nerve-fibres to the 
organs that collect and masticate food, and, in some at least, 
regulates the movements of the body so that the different parts 
move together in harmony. 

In addition to the nerve-ring there is a connected row of gang- 
lions lying below the alimentary canal. This row is connected 
with the ganglion below the esophagus in the nerve-ring. Each 
ganglion in the row sends off nerve-fibres to the part of the body 
near the ganglion, and regulates the movements and other w r ork 
of its own part. 

The highest kind of nervous system.— The highest kind of 
nervous system is found in vertebrate animals, that is, those 



226 PHYSIOLOGY FOR YOUNG PEOPLE 

having a backbone, or spine. Here, too, there is a row of gan- 
glions, called the spinal cord; but, instead of lying below the ali- 
mentary canal, it lies along the back above the alimentary canal, 
and for orotection is placed in the cavity of the spinal column. 




THE BRAIN AS SEEN FROM ABOVE 



In the lowest vertebrate animals there is only the spinal cord, 
with nerve fibres going off in pairs from it to adjacent parts of 
the body. A little higher up in the scale, however, the ganglions 
at the front end of the cord enlarge to form the brain, and nerve- 
fibres go off not only from the ganglions of the spinal cord, but 
also from the brain to sense organs, such as eyes and ears, and to 
other parts of the body. 



PLANT AND ANIMAL IRRITABILITY 



227 




BRAIN OF A DOG 



As the brain increases in size in 
comparison with the rest of the body 
the intelligence of the animal in- 
creases, until the highest degree of 
intelligence is attained in man. In 
man the average weight of the brain is 
estimated to be about one-fiftieth of 
the weight of the rest of the body; in 
birds, about one-hundredth; in fishes 
and reptiles, about one-thousandth. 

The degree of intelligence depends 
not alone on the comparative weight of the brain, but also 
on its structure. The seat of intelligence is that part of the 
brain known as the cerebrum. The nerve-cells of the cere- 
brum, in which all its activity is originated, are placed on 
the outer surface of the cerebrum. As animals rise in the 
scale of intelligence this surface is increased in extent by 
foldings, and consequently affords greater room for nerve-cells. 
This difference of structure is readily ob- 
served in a picture of the cerebrum of a 
rabbit, of a dog, and of a man. In the 
cerebrum of the rabbit faint foldings ap- 
pear; in the dog the foldings are quite 
distinct; but in the cerebrum of man these 
foldings are more numerous and have a 
much greater depth than in the cerebrum 
brain of a rabbit of any other animal. Thus it will be seen 




228 PHYSIOLOGY FOR YOUNG PEOPLE 

that, by reason of the structure and comparative size of his 
brain, man rises in the scale of intelligence far beyond all 
other animals. 

SUMMARY 

1. The two functions of nerves are irritability and control. 

2. All protoplasm is irritable, but the protoplasm of a living nerve-cell 
is more irritable than any other protoplasm. 

3. Irritability in the plant is greatest in the leaf and the tip of the root. 

4. The tip of the root responds to such stimuli as gravity, contact with a 
solid, moisture, heat, and fertile soil. 

5. The leaf responds to such stimuli as light and contact. 

6. The leaves of the sundew and Venus's fly-trap close when insects 
touch them, and so secure needed proteid food. 

7. Even one-celled animals respond to different kinds of stimuli. 

8. The jelly-fish is one of the earliest animals in which nerves have been 
found. 

9. Nerve tissue is made up of cells. 

10. A group of nerve-cells working together is called a nerve-centre, or 
ganglion. 

11. In such animals as the mussel there is a ganglion placed wherever an 
important function is carried on. 

12. In such animals as the earthworm, insects, and the lobster, which 
consist of a succession of parts, there is a nerve-ring around the esophagus, 
and a row of ganglions below the alimentary canal. 

13. In vertebrates, there is a row of ganglions, called the spinal cord, 
above the alimentary canal. 

14. In all but the lowest vertebrates the ganglions at the front end of 
the cord enlarge to form the brain. 

15. Animals rise in the scale of intelligence as the brain increases in 
size in comparison with the rest of the body, and as the foldings of the 
cerebrum become deeper and more numerous. 



CHAPTER XVII 
THE ORGANS OF THE NERVOUS SYSTEM 

Controlling officers. — In every large business there is a 
manager, whose duty it is to give orders and to receive reports. 
In a railway company it would never do to let every engineer 
on the road run his train just when he likes. The running of 
the trains must be under the control of a train despatcher who 
has supreme command. This is necessary in order to avoid 
accidents and to carry on the business of the road to the best 
advantage. 

The despatched office is connected with every station of the 
road by means of telegraph wires. The despatcher can send 
out orders quickly to every station, and can receive reports 
promptly, telling him what is being done. 

The controlling organ of the body.— In order that all the 
organs of the human body may w r ork together for the welfare 
of the body there must be some central power to control their 
action. The brain is this central controlling organ. 

Nerves extend like telegraph wires from the brain to all parts 
of the body, and by means of these nerves the brain can send 
out instantly to any part orders which we call impulses. More- 
over, by means of nerves, impulses come to the brain from any 
part of the body; thus the brain is kept informed of what is 
going on in every part. 

229 



230 



PHYSIOLOGY FOR YOUNG PEOPLE 




THE BRAIN, SPINAL CORD, AND NERVES 



THE ORGANS OF THE NERVOUS SYSTEM 231 

The brain. — The brain is the part of the nervous system 
that is contained in the skull, and is a mass of nerve cells. The 
brain receives a liberal supply of blood. The entire surface is 




THE BRAIN AS SEEN FROM ABOVE 



covered with a layer of blood tubes, which send branches to the 
interior to convey nourishment to the cells. 

This picture gives a view of the upper part of the brain and 
shows the folds of its surface. These folds, or ridges, are called 
convolutions. This part of the brain is divided into a right and 
a left hemisphere by a deep furrow that extends inward to a 
considerable depth. At the bottom of this furrow is a thick 
band of nerve-fibres that pass across from one hemisphere to 



232 



PHYSIOLOGY FOR YOUNG PEOPLE 



the other and help to connect and hold the two hemispheres 
together. In this picture the bands and the parts below are 
cut through, so as to show the different: parts of the brain. The 
upper folded part, which extends from front to back, is called 




SECTION OF BRAIN 

1. Cerebrum. 2. Cerebellum. 3. Medulla oblongata. 

4. Spinal cord. 

the cerebrum. The cerebellum lies under the cerebrum at the 
back. Just in front of the cerebellum is that part of the brain 
that is known as the medulla, or bulb. 

The fibres of the medulla extend downward into the spinal 
cord. As the medulla is connected with the cerebrum and the 
cerebellum above and with the spinal cord below, it unites 
these parts and serves as the connecting link between them. 

Structure of the brain.— The various parts of the brain are 
made up of two kinds of substance, white matter and gray 



THE ORGANS OF THE NERVOUS SYSTEM 



233 



matter. The white matter consists of nerve-fibres only, the 
gray matter of nerve-fibres and nerve-cells. The surface of the 
cerebrum and the cerebellum is covered with a thin layer of 
gray matter, called the cortex. 

The work of the cerebrum. — The cerebrum is the organ of 
intelligence. All acts of the mind are carried on by means of 




AREAS OF CEREBRUM 
1. Spinal cord. 2. Medulla. 3. Cerebellum. 4. Cerebrum 

the cerebrum. It is by means of the cerebrum that we see, 
feel, hear, taste, smell, remember, imagine, reason, and will to 
do things. The cells in the cortex of the cerebrum send out 
impulses to voluntary muscles and cause movement. They 
also receive from different parts of the body impulses that cause 
sensation. 



234 PHYSIOLOGY FOR YOUNG PEOPLE 

Impulses intended for special parts of the body, such as the 
hand or foot, are sent out from particular spots or areas in the 
cortex. In the diagram the part marked foot is concerned in 
the work of sending out impulses that control the movements 
of the foot. In a similar way, the areas marked knee, shoulder, 
finger, etc., are concerned in controlling the movements of 
these parts. Certain other areas of the cortex are concerned 
in receiving impulses from particular parts. The area, for ex- 
ample, marked sight memories is the part of the cortex that 
receives the impulses from the eye and gives rise to the sensa- 
tion of sight. 

The work of the cerebellum. — When the cerebellum is in- 
jured there is a lack of harmony in the movements of the body. 
In the act of walking, some muscles contract to lift the leg and 
foot; others contract and carry them forward. If the first set, 
by a strong contraction, should lift the foot high, while the 
second set, by a feeble contraction, should carry it only an inch 
or two forward, walking would be difficult or impossible. The 
two sets of muscles must act in harmony, both in regard to the 
time and the strength of their contractions. When two or more 
sets of muscles act in harmony to produce a movement they 
are said to be coordinated. The cerebellum is the central 
organ whose work is to coordinate muscular movements. 

The work of the medulla. — One part of the work of the 
medulla is to connect the spinal cord with other parts of the 
brain. But the medulla continually does other important work. 
It contains nerve-cells arranged in groups. One group of nerve- 



THE ORGANS OF THE NERVOUS SYSTEM 235 

cells sends out impulses to control and regulate breathing. 

Whether we are asleep or awake, these nerve-cells send out a 
constant stream of impulses, and breathing goes on without 
interruption. 

The medulla has another group of nerve-cells which send out 
impulses to the involuntary muscles in the walls of the arteries. 
This group regulates the size of the arteries throughout the body, 
so that the tissues and organs may receive more blood w r hen they 
are active and less blood when they are inactive. The amount 
of blood flowing through the brain is diminished during sleep. 
When we go to sleep the arteries in the skin dilate and con- 
tain more blood. Less blood then goes to the brain. When 
we awake, impulses cause the arteries of the skin to become 
smaller and contain less blood. A greater supply of blood 
then goes to the brain while it is working. 

W^hen food comes into the mouth, impulses from the same 
group of nerve-cells in the medulla cause the arteries in the 
salivary glands to dilate and thus supply more blood to the 
gland cells w r hen they are called upon to make an increased 
amount of saliva. 

On a cold day, impulses from this group cause the arteries in 
the skin to contract and the skin contains less blood. Then 
less heat is lost from the surface of the body. On a warm day, 
the arteries of the skin dilate and contain more blood. The 
sweat glands thus receive an increased supply of blood, from 
which they furnish a larger amount of perspiration. As this 
evaporates it helps to cool the body. 



236 



PHYSIOLOGY FOR YOUNG PEOPLE 



The medulla contains also groups of nerve-cells that regulate 
such acts as sneezing, coughing, sighing, swallowing, and closing 
the eyelids. 

Cranial nerves. — There are twelve pairs of nerves that pass 
out from the brain. They are called cranial nerves. Each 

nerve is made up, not 
of a single fibre but of 
many fibres bound 
together in one com- 
mon nerve trunk, just 
as a number of wires 
are bound together to 
form a cable. One 
pair of cranial nerves 
goes to the eyes. An- 
other pair goes to the 
ears. One pair goes 
to the nose. Others 
end in the tongue and 
in the muscles and the 
skin of the face. A 
very important pair, called the pneumogastrics, send some fibres 
down the neck into the thorax to the heart and lungs, other 
fibres extend on into the upper part of the abdomen to end 
in the wall of the stomach and in the liver. 

This picture gives a view of the under surface of the brain, 
and shows where some of the cranial nerves pass out. 




UNDER SURFACE OF BRAIN 
I. -XII. Cranial nerves 



THE ORGANS OF THE NERVOUS SYSTEM 



237 



The spinal cord.— The spinal 
cord extends from the brain down- 
ward for seventeen or eighteen inches 
in the bony canal of the spine. 

The sketch shows how the nerve- 
cells and nerve-fibres of the cord are 
arranged. The outer part is com- 
posed of white 





-2 



—2 



SECTION OF SPINAL CORD AND 
NERVES, FRONT VIEW 

1. Cord. 2. Nerves of anterior root. 
3. Nerves of posterior root 



nerve- 



NERVES OF ARM 
From "Gray's Anatomy" 



matter, the cen- 
tral part of gray 
matter. The 
outer white mat- 
ter is made up of 
nerve-fibres only. 
The central gray 

matter consists of nerve-cells and 
fibres. 

Spinal nerves. — Nerve-fibres pass out 
from the sides of the spinal cord, and are 
called spinal nerves because they are con- 
nected with the cord. There are thirty-one 
pairs of spinal nerves, and they all pass 
outward to end in muscles, skin, and other 
parts of the body. 

This picture shows some of the larger 
nerves of the arm and hand. From these 
larger nerves hundreds of tiny branches 



238 



PHYSIOLOGY FOR YOUNG PEOPLE 




pass off, some to end in the muscles of the arm and the hand, 
others to end in the skin that covers these muscles. The fact 
that it is impossible to prick the finger or arm 
with the point of a needle without touching one 
of these nerves gives some idea of the enor- 
mous number that end in the skin. 

If the larger nerves of the arm were traced 
upward still farther, we could then follow them 
inward toward the spine and see where they 
come out from the spinal cord. They are, in fact, 
simply outward and downward continuations 
of the spinal nerves. 
Here is a picture of the 

NERVES OF FOOT „ , „ 

From' days Anatomy" large nerves ot the toot. 

They are the continuation downward 
of spinal nerves that come out from the 
lower end of the spinal cord. Fine 
branches of these end in the muscles 
and the skin of the leg and the foot. 

In a similar way, nerves from the mid- 
dle part of the cord end in the muscles 
and the skin of the walls of the chest and 
the abdomen. Every muscle fibre and 
every minute portion of skin receives at 
least one tiny branch of a nerve. 

How the nerves are joined to the spinal cord.— This is a 
picture of the spinal cord. It shows how the upper part of 




NERVES COMING FROM THE 
SPINAL CORD 

1. Spinal cord. 2. Posterior 
root. 3. Anterior root. 4 
Spinal nerve 



THE ORGANS OF THE NERVOUS SYSTEM 



239 



the cord is attached to the under surface of 
the brain. 

If the cord were cut across on a level with 
a pair of these spinal nerves it would be 
seen that a bundle of fibres from the front 
meets a bundle of fibres from the back, and 
that the two bundles join just outside the 
cord to form a spinal nerve. Each spinal 
nerve, like a cranial nerve, is made up of 
many fibres bound together. 

The bundle of fibres in front, which is 
called the anterior root, differs from the 
bundle of fibres at the back, which is called 
the posterior root. When, for example, you 
decide to move your index finger, your will 
starts an impulse that travels from the brain 
down the spinal cord, and then out along a 
fibre of the anterior root to the shoulder and 
down the arm to the finger. When the im- 
pulse reaches the proper muscles they con- 
tract and the finger is moved. 

On the other hand, if you prick your 
finger with a needle, an impulse is thereby 
started that travels up the arm along a 
fibre of the posterior root, enters the spinal 
cord, and then passes up the cord to the 
brain. Thus all impulses going inward 
travel by means of the posterior root, 



) — 4 



SPINAL CORD AND 
NERVES, FRONT VIEW 

1. Base of brain. 2, 3. 
Spinal nerves. 4. Sym- 
pathetic ganglion 



240 PHYSIOLOGY FOR YOUNG PEOPLE 

and all impulses going outward travel by means of the 
anterior root. 

Because nerve fibres of the anterior root conduct impulses 
that go to muscles and give rise to motion, these nerves are 
called motor nerves. Because nerve fibres of the posterior 
root conduct to the brain impulses that give rise to sensations, 
these nerves are called sensory nerves. The motor and the 
sensory nerves come together and lie side by side in one common 
nerve trunk soon after they come out of the cord. 

Reflex actions. — The fibres of the posterior root of a spinal 
nerve are connected indirectly in the spinal cord with those of 
the anterior root. A nerve impulse on coming into the cord 
by the posterior root may pass up the cord to the brain and not 
affect the fibres of the anterior root. On the other hand, while 
an impulse is going to the brain, it may, as it enters the cord by 
the posterior root, affect the fibres of the anterior root and start 
a motor impulse. This impulse travels out immediately to 
certain muscles and causes them to contract at once without 
waiting for an impulse from the brain. Movements that are 
produced in this way are called reflex actions. 

Reflex actions serve to protect us from dangers. If the hand 
is accidentally placed on a hot object, it is jerked away quickly, 
even before we have time to think of what we are doing. It 
would take too long for a sensory impulse to travel from the 
hand that is in danger to the brain, and then for the brain to 
comprehend what is going on at the hand and send an impulse 
to the proper muscles to withdraw the hand; so on its way to 
the brain the sensory impulse starts a motor impulse and the 



TIIK ORGANS OF THE NERVOUS SYSTEM 



241 



hand is moved away before the brain finds out what is the 
matter. 

Another illustration of reflex action is seen in the rapidity 
with which the eyelids close to protect the eye from a sud- 
den flash of bright light or from some object coming toward it. 




_l 



NERVES IN SIMPLE REFLEX ACTION 



1. Skin. 2. Sensory nerve cell. 3. Terminations of sensory nerve. 4. Motor 
nerve cell. 5. Motor nerve fibre ending in muscle 

When the sole of the foot is tickled, muscles of the leg con- 
tract to draw it away. These muscles will contract even when 
we do not w r ish them to contract. In many persons when the 
sole of the foot is tickled, muscles of the leg will contract even 
though every possible effort is made to prevent them from 
contracting. During sleep w T hen the sole of the foot is tickled, 



242 PHYSIOLOGY FOR YOUNG PEOPLE 

muscles of the leg contract and draw it away. These facts 
prove that the movements in such cases are brought about in a 
reflex way through the spinal cord, and are not the result of an 
ordinary impulse sent out from the brain. 

The spinal cord, then, has two main functions. It serves to 
conduct impulses from the brain to the spinal nerves, and from 
the spinal nerves to the brain. It serves also the purpose of 
carrying on reflex action. 

Habit. — When we attempt to do anything for the first time, 
we are conscious that we are trying to make some part of the 
body do what we want it to do. If we are learning to skate, we 
are conscious of trying to keep erect and to slide forward on 
the ice. Whenever we are conscious of an attempt to make 
some part of the body do what we want it to do, the movements 
of that part are controlled by nerve centres in the cerebrum. 
But when the movements of some part of the body, as in walk- 
ing, are made without our giving attention to them, the move- 
ments are controlled by nerve centres in some lower part of the 
brain or in the spinal cord. Movements that are made without 
our giving attention to them are said to be reflex. 

When an act that we have to think about is done frequently, 
we gradually have to think less about it than we did at first, 
and in time we may be able to do it unconsciously. When we 
were learning to walk, we had to give attention to every move- 
ment we made; but now we start in a certain direction and 
never think of when we should lift a foot or put it down. If 
friends are with us, we talk, and laugh, and think of many other 



THE ORGANS OF THE NERVOUS SYSTEM 243 

things, hut never think of how we are walking. As soon as 
one foot touches the ground sensory impulses start from the 
foot along nerves toward the brain. When they reach a cer- 
tain lower centre, motor impulses are started which cause 
muscles to raise the other foot. Walking thus becomes a 
series of reflex acts controlled by lower nerve centres. 

In learning to write, to sew, to play a piano, to operate a 
typewriter, or to do anything else that requires repeated effort 
in learning, we have an experience similar to that in learning 
to walk. At first nerve impulses that cause movements travel 
along nerves with difficulty, for the path of the impulses is a 
new one. The movements are slow and deliberate. We are 
conscious of an attempt to make them, for they are controlled by 
nerve centres in the cerebrum. As, however, similar impulses 
travel again and again along nerves, they travel with less and 
less difficulty. The path is more easily traversed, for nerves 
tend to act more and more readily in the way in which they 
have acted before. In time the movements are so easily made 
that lower nerve centres are able to control them without the 
aid of the cerebrum, and the movements become reflex. The 
cerebrum is then free to attend to something new. 

It is a very great advantage to us that lower nerve centres in 
time take control of movements that at first were controlled 
by centres in the cerebrum. It would be impossible to acquire 
skill in any kind of work if oft-repeated movements required 
the same conscious control that they require at first. 

When, because of frequent repetition, a tendency to act in a 



244 PHYSIOLOGY FOR YOUNG PEOPLE 

given way becomes fixed, we say that a habit has been formed. 
The body, or a part of it, is then ready to carry on at once its 
accustomed movements whenever the usual stimulus excites it. 
It has been truly said that we are largely a bundle of habits. 
We necessarily get into certain ways of doing things because we 
do the same thing so often. It is important, therefore, that in 
our first attempts to do a thing we should be careful to do it in 
the best way possible, in order that the best way may become a 
fixed habit. 

The name habit is given also to many other tendencies be- 
sides those of movement. Among these are habits of manner 
of living, such as cleanliness and tidiness; habits of mind, such 
as being careful and exact; habits of conduct, such as industry, 
temperance, and truthfulness. All habits, both good and bad, 
are formed by frequent repetition; and the oftener the act that 
gives rise to a habit is repeated the more fixed does the habit 
become. It frequently happens that a harmful habit is formed 
that one would gladly break away from. One of the best ways 
of breaking away from a bad habit is to practise repeatedly 
something good that can take its place, in order that a good 
habit may replace the bad one. 

The sympathetic nerves. — In addition to the spinal and the 
cranial nerves, there is another distinct set that branches off 
from the spinal nerves to end in various internal organs and in 
the walls of the blood tubes. These are called sympathetic 
nerves. A branch from a spinal nerve joins a little knot, or 
cluster, of nerve-cells just outside the spinal cord, as shown in 



TIE ORGANS ov THE NERVOUS SYSTEM 245 




SYMPATHETIC NERVES AND PLEXUSES 
1 A spinal nerve. 2. A sympathetic ganglion. 3. The solar plexus 



246 



PHYSIOLOGY FOR YOUNG PEOPLE 



*^ 



the picture below. This knot is known as a ganglion of the 
sympathetic system. There is on each side of the spinal cord 
a row of sympathetic ganglions connected with one another by 
nerve fibres. 

The picture on page 239 show^s a row, or chain, of ganglions 
on one side of the spinal cord. There is a similar row on the 

other side of the cord. 

From these small gan- 
glions nerve fibres pass to 
join a large mass of nerve 
cells and nerve fibres 
known as a plexus. One 
of these is the great solar 
plexus situated behind 
the stomach. Another 
plexus is situated near 
the heart and is known 
as the cardiac plexus. 
Another in the neck is called the cervical plexus, and still 
another in the pelvis is called the pelvic plexus. These four 
great plexuses are situated in front of the spine. Great num- 
bers of sympathetic nerve-fibres pass off from them to end in 
the involuntary muscles of various parts, such as the walls of 
the stomach, intestine, and blood tubes. 

The sympathetic system, with its ganglions and plexuses of 
nerve-cells and nerve-fibres, may be considered as a develop- 
ment, or expansion, of one part of the spinal nerves. The office 




SYMPATHETIC GANGLION AND 
SPINAL NERVE, RIGHT SIDE 

1. Spinal cord. 2. Posterior root. 
3. Anterior root. 4. Spinal nerve. 
5. Sympathetic ganglion. 6. Nerve 
fibres connecting sympathetic 
ganglion with spinal nerve 



THE ORGANS OF THE NERVOUS SYSTEM 247 

of the sympathetic system is to supply nerve-fibres to involun- 
tary muscles in all parts of the body for the control and regula- 
tion of their movements, and to supply nerve-fibres to the 
secreting glands for the purpose of controlling and regulating 
their periods of rest and work. 

Hygiene of the nervous system.— The nervous system re- 
quires a constant and generous supply of pure rich blood in 
order that it may do its work well. When the blood becomes 
impoverished on account of an insufficient amount of food, or 
from any other cause, the brain suffers from starvation. 

If for any reason the heart-beats become so feeble that a 
much smaller stream of blood than usual is sent to the brain, 
a sensation of faintness is felt. Total loss of consciousness 
follows quickly if this condition continues. The cerebrum 
cannot do its work unless it has a sufficient supply of blood. 

The brain is very sensitive to the presence of poisons in the 
blood flowing through it. Impure air affects the brain. An 
excess of carbon dioxide, or a diminished amount of oxygen in 
the air we breathe, gives rise to headache and drowsiness and 
interferes with the normal working of the brain. 

Exercise of the brain. — The brain, like the muscles, needs 
exercise. Physical work strengthens the muscles and gives us 
increased physical power; mental work develops the brain and 
gives us increased mental power. In order to develop the 
brain, mental work should be done in a regular, systematic way. 

Intense brain work of any kind, if prolonged, exhausts the 
supply of food contained in the blood and impairs the whole 



248 PHYSIOLOGY FOR YOUNG PEOPLE 

system. Pupils with frail bodies and bright minds should be 
careful to avoid prolonged mental effort. Only those that have 
well-developed, vigorous bodies should ever be allowed to com- 
pete for prizes given as a reward for study. 

Too much time is often given to the mere study of books. 
An occasional day may be spent w T ith profit among the hills, 
studying the rocks, springs, and soils; or in the woods, enjoy- 
ing the trees, birds, and flowers. 

Brain rest. — Regular times for rest, as well as regular times 
for work, are necessary, in order to have a healthy, vigorous, 
nervous system. The brain and nerves need rest just as mus- 
cles need rest. If muscles that have been vigorously exercised 
are tired, stiff, or sore after a reasonable period of rest, the. 
exercise was too severe or too prolonged. Mental work, such 
as hard study, exhausts the brain and gives rise to a feeling of 
fatigue that should entirely pass away after a period of rest and 
sleep. If the following morning does not find us refreshed and 
able to renew our study with comfort, the mental work of the 
day before was too severe or too prolonged. 

Brain rest does not mean a state in which the brain ceases to 
do any work, for during waking hours it is always working, 
and even while we are asleep it is not entirely inactive. One 
way to rest the brain is to change from our regular work for a 
short time to something else that will afford pleasant relaxation. 
It has been found by experience that even short periods of re- 
laxation, if spent in the fresh air and accompanied by bodily 
activity, will do much to rest the brain and restore it to its 



THE ORGANS OF THE NERVOUS SYSTEM 249 

normal vigor. After a period of hard mental effort the mind 
will find rest in games such as tennis or basket-ball, or in light 
gardening. Indoor games, inexpensive pastimes, cheerful com- 
panionship, music, and various other forms of entertainment 
afford suitable recreation after the care and toil of the day. 

Sleep. — Sleep furnishes the most complete and perfect rest 
for mind and body. Some persons need more sleep than others. 
Those that do mental work require more sleep than those that 
are engaged in physical work. Most grown people require 
from seven to nine hours of sleep a day. Children, however, 
need more sleep than grown people do. At the age of four 
years, eleven or twelve hours of sleep are required; from the 
ages of six to ten years, ten or eleven hours should be given to 
sleep; and from ten to sixteen years, nine hours of sleep are 
required. 

Regular hours for going to bed and for rising favor sleep. If 
one has good health, exercise in the open air, suitable games, 
and work that is not too laborious are also favorable to sleep. 
Fatigue, if it is not too severe, promotes sound, refreshing sleep, 
while idleness prevents it. 

Among the many ways in which sleep may be disturbed are 
indigestion, lack of fresh air in the sleeping-room, excessive bed 
clothing, or cold feet. Sleep may be disturbed also by dis- 
tressing dreams, which are sometimes caused by exciting stories 
read or heard just before bed-time, or by play that is too ex- 
citing in the evening. Worry is a frequent cause of disturbed 
sleep. One is fortunate if he can dismiss all cares from his 



250 PHYSIOLOGY FOR YOUNG PEOPLE 

mind when he rests his head on his pillow. Every one should 
try to cultivate this habit. 

Boys and girls in school are sometimes expected to do as 
home-work tasks that are too difficult for them. After an 
evening spent in unsuccessful efforts to solve a number of long 
and difficult problems in arithmetic, or to unravel a number of 
involved sentences in grammar, the mind is liable to be too 
much excited for restful sleep. The consequence of failure in 
class often adds to the worry and renders sound, refreshing 
sleep impossible. All tasks that are required of children, both 
at school and at home, should be difficult enough for earnest 
effort in their performance, but .should not be so difficult as to 
discourage a child by requiring what is beyond his power to 
accomplish. 

Headache. — The most common causes of headache are eye- 
strain, indigestion, constipation, worry, and breathing bad air. 
Eye-strain is probably the most common cause of constant or 
recurring headaches. The muscles or nerves of the eye often 
become fatigued from improper use of the eye, or from some 
defect in the eyeball, such as near sight or far sight. When 
eye-strain is due to a defect of the eyeball, it may be lessened 
or overcome, and the headache be prevented, by the use of 
spectacles that are accurately and carefully adjusted. 

Another cause of headache is indigestion from improper food, 
such as unripe fruits, or pastry, from overloading the stomach, 
and from the habit of swallowing food without taking time to 
chew it well. Headaches from such causes may be prevented 



THE ORGANS OF THE NERVOUS SYSTEM 251 

by eating a proper amount of suitable food at regular intervals, 
and by taking time to chew it thoroughly. 

Undigested portions of food are not absorbed, but pass out 
of the intestine as useless material. If the intestine is not re- 
lieved of this useless material at proper intervals, the condition 
is called constipation. Constipation is a cause of headache, 
dulness, fretfulness, and disturbed sleep, and is frequently the 
result of indigestion. Care should be taken to establish the 
habit of getting rid of this useless material every day. 

SUMMARY 

1. The brain is the controlling organ of the body. 

2. By means of nerves, the brain sends out orders to all parts of the 
body, and also receives messages from them. 

3. The upper part of the brain, or cerebrum, is divided into two hemi- 
spheres. 

4. The cerebrum is the organ of intelligence. 

5. Impulses from certain areas of the cortex go out to particular parts 
of the body. 

6. Impulses from different parts of the body are received at different 
areas of the cortex. 

7. The function of the cerebellum k to coordinate muscular movement. 

8. Among the functions of the medulla are the control of breathing, 
and the regulating of the size of arteries and consequent supply of blood to 
different organs. 

9. Cranial nerves pass out from the brain; spinal nerves pass out from 
the spine. 

10. The nerve-fibres of the anterior root of a spinal nerve conduct im- 
pulses outward, and are called motor nerves. 

11. The nerve-fibres of the posterior root of a spinal nerve conduct 
impulses inward, and are called sensory nerves. 



252 PHYSIOLOGY FOR YOUNG PEOPLE 

12. There are two principal functions of the spinal cord: to conduct 
impulses, and to carry on reflex actions. 

13. The sympathetic nerves branch off from the spinal nerves and end 
in different internal organs and in the walls of the blood tubes. 

14. A mass of sympathetic nerve-cells and nerve-fibres is called a plexus. 

15. Faintness, or unconsciousness, may arise if there is not a sufficient 
supply of blood to the brain. 

16. Exercise of the brain strengthens it. 

17. The brain and nerves need rest. The best rest is obtained from 
sleep. 

18. Two common causes of headache are indigestion and eye-strain. 



CHAPTER XVIII 

THE EFFECTS OF NARCOTICS ON THE NERVOUS 

SYSTEM 

Effects of alcohol. — Alcohol is especially harmful to the 
tissues of the nervous system, the delicate cells of the brain being 
easily injured by it. When a moderate amount of alcohol is 
taken there is, at first, a feeling of mild excitement. The 
mind appears then to work more rapidly and easily than usual. 
For this reason some are led to believe that alcohol enables 
them to think better and more quickly. 

It has, however, been proved by careful experiments that 
alcohol enables the mind to work more rapidly only in the sim- 
plest forms of mental work, such as the recognizing of signs 
displayed for that purpose, and then only for a short time. 
After a brief lapse of time there is a slowing down of the mind 
even in performing the simplest mental acts. In more difficult 
acts that require comparison, memory, or judgment, the mind 
works more slowly from the beginning, although the person 
thinks his mind is working more rapidly. A common effect of 
alcohol, when taken in small quantities, is to deceive those who 
take it. They feel that the brain is extraordinarily active, and 
that they are thinking more rapidly than usual, whereas they 

are really thinking more slowly than usual. 

253 



254 PHYSIOLOGY FOR YOUNG PEOPLE 

In such cases the harmful effect of alcohol on the protoplasm 
of the brain cells is similar to the action of ether, chloroform, 
and other narcotics that dentists and surgeons use to make 
people unconscious. When these drugs are beginning to para- 
lyze the brain cells, the patient often feels that he is stronger and 
that his mind is more active than usual. 

When alcohol is beginning to injure the brain cells, the first 
powers of the mind to be lost are the finer ones of judgment and 
reason. These preserve what is called the " normal balance of 
the'brain," and serve to put restraint upon our actions. It is 
by means of these powers that we consider the prudence and 
propriety of our actions. When a small amount of alcohol is 
taken these powers are impaired temporarily. The usual re- 
straint is gone, and a man becomes reckless, saying and doing 
things he would not if the cells of his brain were not injured 
and made incapable of doing their usual work. The power of 
judgment, too, is lost. A man will think he is singing well or 
speaking eloquently, while those around him cannot help a 
feeling of pity because the alcohol has so unbalanced his mind. 
It is because of this impaired judgment that a man is deceived 
and led to think his mind is working more rapidly after taking 
a small amount of alcoholic liquor, whereas all the time it is 
working more slowly. 

If the amount of alcohol is sufficient to produce intoxication, 
the nerves that control muscles will next be injured. Speech 
will then become thick, the gait will be unsteady, and the move- 
ments of the eyes and eyelids in winking and seeing will be ir- 



EFFECTS OF NARCOTICS OX NERVOUS SYSTEM 255 

regular. The sense of touch and other special senses will be 
blunted, and there will be a tendency to sleep. If a very large 
amount of alcohol is taken the nerve centres in the medulla that 
control circulation and breathing may be paralyzed, and the 
result may prove fatal. 

Another evidence of injury to the brain cells of one who has 
acquired an appetite for alcoholic liquors is the weakened state 
of his will. As the habit grows upon him, his will power be- 
comes weaker and weaker until it seems impossible for him to 
muster up sufficient determination to break away from the habit 
which he knows is destroying him. 

Life insurance and alcohol.— In England, Scotland, Can- 
ada, and Australia, there are life insurance companies that 
separate their business into two sections. In one section they 
insure lives of abstainers, i. e., those who do not drink alcoholic 
liquor. In the other section they injure lives of moderate 
drinkers of alcoholic liquor. In all these companies it has been 
found that, on the average, abstainers live longer than moderate 
drinkers. This result would not mean so much if the com- 
panies were careless in insuring moderate drinkers. They are, 
however, so careful that the average life of the moderate drinkers 
they insure is as long as the average life of the men that are 
insured in other companies that make no distinction between 
abstainers and moderate drinkers. 

As a result of long experience, insurance companies have 
made up what are called tables of mortality. These tables 
show how many of a given number of persons having the same 



256 PHYSIOLOGY FOR YOUNG PEOPLE 

age may be expected to die each succeeding year. From these 
tables the companies estimate the yearly expenses they will have 
to meet because of death. 

The largest of the companies that insure in two sections is the 
United Kingdom Temperance and General Provident Institu- 
tion, of London, England. This company estimates the number 
of expected deaths by using the same tables of mortality that 
other insurance companies use. During forty-one years — 1866 
to 1906 inclusive — the number of expected deaths in the ab- 
stainers' section was 10,889, while in the section of moderate 
drinkers it was 13,952. The actual number of deaths among 
the abstainers was 7,760, or 71.26 per cent, of the expected 
number. Among the moderate drinkers the actual number of 
deaths was 13,188, or 94.52 per cent, of the number expected. 
The rate of death, therefore, among the moderate drinkers was 
nearly one-third greater than the rate among the abstainers. 

In these companies the longer life of abstainers is recognized 
in a business way. Some of them insure abstainers at a lower 
rate than they insure moderate drinkers; others insure at the 
same rate in both sections, but pay a larger share of profits to 
the abstainers. 

Tobacco. — Tobacco is a mild narcotic. It contains a small 
amount of a powerful poison called nicotine. In chewing, the 
saliva dissolves out part of the nicotine, and it passes through 
the mucous membrane lining the mouth into the small blood 
tubes, where it mingles with the blood. In smoking, some of 
the nicotine is changed to vapor, while part of it is changed into 



EFFECTS OF NARCOTICS ON NERVOUS SYSTEM 257 

an even more powerful poison called pyridine. Some of these 4 
poisons in the smoke pass into the small blood tubes of the 
mouth, and so mingle with the blood. 

Tobacco does not affect all people in the same way. When 
it is first used its poisonous effect is often very marked; but 
many persons soon become accustomed to its moderate use, and 
do not suffer any immediate injurious effect. Still, the moderate 
use of tobacco for years may give rise to serious consequences, 
and it is probable that most grown persons would feel better if 
they did not use it. 

There are, on the other hand, many whose bodies cannot 
resist the poison of tobacco, and its use gives rise to a trembling 
of the hands and limbs, to giddiness, sleeplessness, catarrh of 
the mucous membrane of the throat, indigestion, or irregular 
beating of the heart. These symptoms disappear when the use 
of tobacco is discontinued. 

It is said by eminent physicians that a chance sore in the 
mouth from biting the tongue or cheeks, or from some sharp 
tooth, is frequently so irritated by the poison of tobacco that a 
cancer is produced at the injured part. 

It is well known also that the use of tobacco may cause a dis- 
ease of the optic nerve at the back of the eyeball and cause 
either impaired vision or total blindness. 

It is quite certain that the use of tobacco in any amount and 
in any form is injurious to young growing persons. The im- 
mature nervous system is unable to resist its poisonous effects. 
The injury from tobacco is greatest when it is used by boys of 



258 PHYSIOLOGY FOR YOUNG PEOPLE , 

tender years. Yet in colleges, where young men are approach- 
ing maturity, the injurious effect of the usfc of tobacco is readily 
observed. In Yale and other colleges, careful measurements 
have shown that growth in weight, height, and girth of chest 
is greater among students that do not use tobacco than among 
those that do use it. 

Cigarettes. — Cigarettes are a great evil, for they enable 
young persons to acquire easily the habit of using tobacco. 
The harmful effects that cigarettes produce are due solely to 
the nicotine that they contain. 

The smallness and mildness of cigarettes conceal their capa- 
city for doing harm. When a boy begins the use of tobacco by 
chewing, or by smoking a pipe or cigar, he usually experiences 
very uncomfortable feelings because of nicotine poisoning. 
Faintness, dizziness, nausea, extreme weakness, and vomiting 
are some of the more usual effects. But the first cigarette, on 
account of its smallness and mildness, seldom gives rise to 
these deathly feelings. In a short time, one cigarette fails to 
satisfy the smoker, so he gradually comes to smoke a great 
number, and thus a large amount of nicotine is absorbed 
each day. 

In the case of some drugs, if the ordinary dose is divided into 
a number of equal parts, and one part is given every ten min- 
utes until all are given, the effect produced is much more power- 
ful than it would be if all were given at once. This is the case 
with nicotine. The dose of nicotine in each cigarette is small, 
but, by its frequent repetition in smoking a number of cigar- 



EFFECTS OF NARCOTICS ON NERVOJJS SYSTEM 259 

ettes in a short time, the poisonous effect of the nicotine is 
greatly increased. 

The amount of nicotine that is absorbed depends upon the 
extent of surface with which the smoke comes in contact. 
Cigarette smokers, as a rule, inhale the smoke so that it comes 
in contact with the mucous membrane not only of the mouth, 
but also of the larynx, windpipe, and larger bronchial tubes. 
The surface , therefore, that smoke comes in contact with when 
it is inhaled is about three times as great as in ordinary smoking. 
The small cigarette, then, is not so weak as it appears. 

When we remember the number of cigarettes that are often 
smoked in one day, the increased effect from frequently repeated 
doses, and the extra amount of poison that is absorbed through in- 
haling the smoke, it is not hard to see why cigarettes bring ruin to 
so many of the unfortunate boys that become addicted to them. 

Tobacco and the heart. — Tobacco often affects the nerves 
that control the beating of the heart. The leading symptom in 
this condition is palpitation. In its mildest forms there is a 
slight fluttering and a sense of discomfort about the heart. In 
more severe attacks the beating of the heart is at times weak 
and irregular; at other times it is stronger and more rapid than 
usual and may be accompanied with considerable pain. These 
uncomfortable symptoms disappear very quickly when the use 
of tobacco is discontinued. 

Narcotics. — Drugs that numb the brain are called narcotics. 
They lessen the power to feel and think, and in large doses 
produce sleep. 



260 PHYSIOLOGY FOR YOUNG PEOPLE 

Opium is a familiar example of a drug belonging to this 
class. Nicotine is a powerful narcotic. Alcohol, also, is a 
narcotic, for, as we have learned, in large quantities it produces 
sleep, and in smaller amounts it numbs the brain and nerves. 

Some narcotics are useful as medicines to relieve pain, but 
they all tend to injure the health if taken habitually. The 
greatest danger connected with the use of small doses of nar- 
cotics is their power to create an irresistible craving for more. 
This makes it difficult, or almost impossible, to discontinue 
their use after the habit of taking them is once formed. 

Opium. — The principal drugs made from opium are lau- 
danum, morphine, Dover's powders, and paregoric. They all 
relieve pain and give a feeling of comfort. This feeling soon 
passes off and is followed by depression and a feeling of weak- 
ness, which makes it easy to repeat the dose in order to secure 
relief. In this way, the habit of taking any of these drugs may 
become fixed before one is aware of his danger. Efforts to 
break off the habit are very often not successful, for narcotics 
injure the cells of the nervous system and weaken the power 
of the will. 

Danger of giving opium to children.— Opium in the form 
of laudanum or paregoric is sometimes given to infants to 
quiet them when crying, or to cause them to sleep. Soothing 
syrups, teething powders, and cordials usually contain opium in 
some form, and for this reason they should never be given to 
infants or children. They simply numb the brain, and take 
away, for a short time, the power to feel pain. Children are 



EFFECTS OF NARCOTICS ON NERVOUS SYSTEM 261 

often seriously and even fatally injured by such use of opium or 
drugs that contain it. No medicine containing opium in any 
form should ever be given to a child except by the advice of a 
physician. 

Chloral hydrate, cocaine, bromides, and headache pow- 
ders. — These drugs may be useful as medicines when properly 
given, but they are liable to do great harm if used by those who 
are ignorant of their action. Moreover, the temptation to re- 
peat the dose makes it easy to form the habit of taking them. 
The only safe rule regarding all such drugs is to let them en- 
tirely alone unless they are prescribed by a physician. 

The following is quoted from the New York Times of August 
5, 1906, and is part of an interview with Luther Burbank by 
Champ Andrews: 

" ' Do you think that whiskey and tobacco impair the faculty for 
work ? ' I asked. He replied: ' If I answered your question simply 
by saying that I never use tobacco and alcohol in any form, and 
very rarely either coffee or tea, you might say that was a personal 
preference and proved nothing. But I can prove to you most con- 
clusively that even the mild use of stimulants is incompatible x with 
work requiring accurate attention and definite concentration. To 
assist me in my work of budding — work that is as accurate and 
exacting as watchmaking — I have a force of some twenty men. I 
discharge men from this force at the first show of incompetency. 
Some time ago, my foreman asked me if I took pains to inquire into 
the personal habits of my men. On being answered in the negative, 
he surprised me by saying that the men I found unable to do the 
delicate work of budding invariably turned out to be smokers and 



262 PHYSIOLOGY FOR YOUNG PEOPLE 

drinkers. Even men who smoke one cigar a day I cannot entrust 
with some of my delicate work. Cigarettes are even more damaging 
than cigars, and their use by young boys is little short of criminal/ " 

According to the letters given below, the Hon. Willard H. 
Olmsted, Judge in the Children's Court of New York, and the 
Hon. Richard S. Tuthill, Judge in the Juvenile Court of Chicago, 
find that cigarette smoking is common among the boys that are 
brought before them for trial. It is a fair inference that the 
habit of smoking cigarettes is, in no small measure, responsible 
for the anaemic, poorly nourished condition of those boys. 

New York, January 11, 1909. 
Dear Sir: — I have yours of January 6, making inquiry concern- 
ing the effects of cigarette smoking in the matter of children who 
are so unfortunate as to be arraigned in the Children's Court. 

Not being a physiologist, it would be difficult for me to determine 
whether cigarette smoking is a cause or an effect. It is certainly a 
fact, however, that I have found cigarette smoking prevalent among 
delinquent children, and in most cases children who were addicted 
to that habit were apparently anaemic and ill-nurtured. 

I am, 

Very truly yours, 

Willard H. Olmsted. 

Chicago, III., January 19, 1909. 
Dear Sir: — An experience with delinquent children, especially 
with delinquent boys, extending over a period of more than twenty 
years, (1) as president of a city shelter and school for the homeless, 
runaways, and strays found in a great city; (2) as Judge for ten 
years of the Juvenile Court from its creation in 1899; and (3) as a 



EFFECTS OF NARCOTICS ON NERVOUS SYSTEM 263 

trustee of the St. Charles School for Boys, a State farm caring for 
delinquent boys from one hundred and two counties of the State, 

warrants me in saying that I have 4 found the pernicious habit of 
cigarette smoking among these boys almost universal. 

The great majority of them have been apparently anaemic and ill- 
nurtured, and I have observed in them a retarded and interrupted 
growth physically, morally, and mentally. 

Very truly yours, 

Richard S. Tuthill. 

SUMMARY 

1. The delicate cells of the brain are easily injured by alcohol. 

2. The drinking of even small amounts of alcohol lessens the working 
power of the mind. 

3. In intoxication, the earliest injury to the brain impairs the finer 
mental powers of judgment and reason. 

4. The nerves that control muscles are the next to be injured. 

5. The drinking of a large amount of alcohol may affect the nerve 
centres that control circulation and breathing, and may cause death. 

6. The continued use of alcoholic liquor may destroy the power of the 
will. 

7. Tobacco contains a powerful poison called nicotine. 

8. Nicotine interferes seriously with growth. 

9. The most harmful form of tobacco is the cigarette. 

10. Tobacco may Injure the nerves that control the beating of the heart. 

11. The use of any narcotic drug may give rise to a strong craving for it. 



CHAPTER XIX 
THE FIVE SPECIAL SENSES 

Information from the outside world.— You will remember 
that the brain receives information from all parts of the body. 
It receives information also in regard to what is happening 
outside the body. The ends of some nerves lie just under the 
scarf-skin, the ends of some are in the tongue, some are in the 
nose, some are in the eyes, some in the ears. Anything from 
the outside world that acts on these nerves starts an impulse 
which they conduct to the brain. There are five different sets 
of nerves over which impulses thus come to the brain. We say, 
therefore, we have five special senses — touch, taste, smell, sight, 
and hearing. It sometimes happens that nerves leading from 
some organ of the body to the brain are injured so that they 
will not conduct an impulse to the brain. It may be that the 
nerves that conduct impulses from the eyes to the brain become 
unable to do their work. Then we are blind, and we get through 
our eyes no idea of the things that other people see. 

While it is by means of our nerves and brain that we touch, 
taste, smell, hear, and see, yet the arrangement of the nerve 
endings is so different for each sense that each must be con- 
sidered by itself. 

The sense of touch. — Objects that make pressure on the 

skin start impulses in nerve endings in the skin. These im- 

264 



THE FIVE SPECIAL SENSES 265 

pulses go from the skin to the brain along sensory nerves, and 
in the brain the impulses give rise to sensations of feeling. By 
means of such sensations we learn much regarding the nature 
of objects that are in contact with the skin. We learn, among 
other things, whether an object is rough or smooth, hard or soft, 
hot or cold. We also learn of its surface, edges, size, shape, and, 
to some extent, of the material of which it is composed. Ex- 
cessive pressure, heat, or cold gives rise to sensations of pain. 
Slight pressure, as with a feather, produces a sensation which 
we call tickling. 

All parts of the skin are sensitive to contact and pressure, 
but some parts are more sensitive than others. The most sen- 
sitive parts are the tips of the fingers, lips, tip of the nose, and 
palms of the hands. Nerve endings are more numerous in the 
skin of these parts than in the skin of less sensitive parts. 

Muscular sense. — Impulses reach the brain from the mus- 
cles. From such impulses we gain a knowledge of the condi- 
tion of our muscles and know to what extent they are contracted. 
In lifting objects we are able to judge of their weight by the 
amount of resistance offered to the muscles as they contract. 

The sense of taste. — The organs of the sense of taste are 
the tongue and the back part of the mouth. These parts, like 
the skin, contain little raised points called papillae. From eight 
to twelve large papillae can be seen at the back of the tongue. 
They are arranged in the form of the letter V. Many smaller 
ones are scattered over the sides and the tip of the tongue, and 
also on the palate and the back part of the mouth. Nerve- 



266 



PHYSIOLOGY FOR YOILNG PEOPLE 




THE TONGUE AND PAPILLAE 

onion from a piece of 
apple when placed on 
the tongue. 

The sense of smell. — 
The fibres, or branches, 
of the nerves of smell, 
called the olfactory 
nerves, are spread out 
on the soft lining of the 
upper part of each nos- 
tril. They extend from 
the brain to the lining of 



fibres end in these papillae and con- 
duct to the brain impulses that give 
rise to sensations of taste. 

We are unable to taste solids. 
They must be dissolved in saliva or 
other liquid before they can be tasted. 

The four principal sensations of 
taste are bitter, sweet, acid or sour, 
and salt or saline. Such substances 
as onions, which have a strong odor, 
are recognized in the mouth by their 
odor and not by their taste. When 
the nose is held tightly, so as to inter- 
fere with the sense of smell, it is diffi- 
cult, or impossible, to tell a piece of 




END OF OLFACTORY NERVE AND ITS 

BRANCHES 

1. Nerve. 2. Branches 



THE FIVE SPECIAL SENSES 



207 



the nose. Sensations of smell are produced by the action on the 
olfactory nerve-fibres of gaseous, odorous substances in the air 
we breathe. During inspiration a current of air streams 
through the nasal passages and the odorous substances it con- 




<4i *- 

SECTION OF EAR 



tains come in contact with the nerve endings in the soft lining 
of the nose. Impulses travel along the nerves to the brain and 
give rise to sensations of smell. 

Some injurious gases in the air we breathe may be detected by 
the sense of smell. This sense, aided by the sense of taste, 
assists us in the selection of food, and is, moreover, a source of 
considerable pleasure. 

The sense of hearing. — The auditory nerves end in the ears. 
They conduct impulses from the ears to the brain. When these 
impulses reach the brain they give rise to sensations of sound. 



268 



PHYSIOLOGY FOR YOUNG PEOPLE 



For convenience of description the ear is divided into three 
parts, the external, the middle, and the internal ear. 

This picture shows how these parts are arranged in relation 
to one another. The external ear consists of the visible part, 
which is commonly meant when one speaks of the ear, and a 







MIDDLE AND INTERNAL EAR 

1. External ear. 2. Drum membrane. 3. Middle ear. 4. Eustachian 
tube. 5. Interior ear. 6. Stirrup bone and membrane to which 
it is attached 

canal extending inward a little more than an inch to a membrane, 
called the drum membrane, which completely separates the 
external from the middle ear. 

The middle ear, or drum, is a small cavity in a bone on the 
side of the skull, and lies between the external and the internal 
ear. The middle ear resembles a drum because it has this 
drum membrane stretched across its outer end like a head of a 
drum. In the middle ear is a chain of three small bones— the 
hammer, the anvil, and the stirrup. The hammer is fastened 



THE FIVE SPECIAL SENSES 269 

to the drum membrane; the anvil comes next, lying between 
the other two; and the stirrup connects at its outer end with the 
anvil, at its inner end with the membrane that is stretched 
across a small opening into the internal ear. 

The middle ear contains air which enters from the throat by 
the Eustachian tube. The drum membrane needs air on both 
sides of it so that it may vibrate freely. If the air pressed on 
the outside only, the membrane could not vibrate. 

The internal ear is called the labyrinth, because it is so com- 
plicated in arrangement. It consists of three parts, or cavities 
— the semi-circular canals above, the vestibule in the centre, and 
the cochlea, or snail-shell below. All these cavities are con- 
nected with one another, and are filled with a watery fluid called 
lymph. 

The auditory nerve divides into three main branches. One 
branch enters each part of the internal ear. The fine endings 
of the nerve float in the lymph. 

By following the pictures closely it is easy to understand how 
each part assists in the production of sensations of hearing. 
Sound-waves, i.ve. s vibrations of air, enter the external ear and 
strike against the drum membrane at the inner end of the 
canal. This causes the membrane to vibrate. The vibrations 
of the drum membrane set the small bones of the middle ear in 
motion. The movements of these bones cause" vibrations of 
the membrane that closes the opening into the internal ear. As 
this membrane vibrates it beats against the lymph in the internal 
ear and causes little wave movements of the lymph. The waves 



270 PHYSIOLOGY FOR YOUNG PEOPLE 

of lymph, beating against the auditory nerve endings, start im- 
pulses that travel to the brain and give rise to sensations of 
hearing. 

Care of the ears. — The best way to care for the ears is to 
leave them entirely alone. The outer end of the canal of the 
external ear may be cleaned when necessary, with a soft, damp 
cloth. Nothing else should be put into the ears under any cir- 
cumstances unless by the advice of a physician. 

The canal is lined with skin that contains glands. These 
glands secrete the ear wax. Usually the wax does not accu- 
mulate but passes out of the canal as it is secreted. Occasion- 
ally, however, the wax remains in the canal, and, forming a 
plug, interferes with hearing. 

Such foreign bodies as peas, beans, buttons, wads of paper, 
and the like sometimes get into the ears. Bugs and insects 
occasionally crawl into the ears. The wisest course under these 
circumstances is to consult a physician, instead of making a bad 
matter worse by clumsy attempts to remove the intruding object. 

If the aid of a physician cannot be obtained, warm water may 
be carefully and slowly injected, without force, into the canal. 
Use an ear syringe for this. Care must be taken to place the 
nozzle of the syringe so as to direct the stream between the object 
and the skin, and not directly against the object, or it will be 
driven farther in. Never attempt to remove anything from the 
ear with a match, pin, lead-pencil, knitting-needle, or any 
similar instrument. 

A blow on the ear with the palm of the hand may rupture a 



THE FIVE SPECIAL SENSES 271 

drum membrane and diminish the power of hearing for life. 
Children sometimes shout in each other's ears in play. They 
should not do this. 

The sense of sight. — The eye is the organ of sight. This 
picture shows the arrangement of the various parts of the eye- 




THE COATS OF THE EYE 



ball. The wall at the back is made up of three distinct coats, 
the sclerotic, the choroid, and the retina. 

The optic nerve enters from behind and the fibres are spread 
out in the retina or inner coat. The interior of the eye con- 
tains a watery fluid, called the aqueous humor, the lens, and a 
jelly-like substance, called the vitreous humor. 



272 PHYSIOLOGY FOR YOUNG PEOPLE 

Parts of the eyeball.— The outer coat of the eyeball has 
two names: the cornea, for the front part, and the sclerotic,. for 
the back part. The cornea is transparent like glass, and bulges 
slightly forward like the crystal of a watch. The sclerotic, or 
white of the eye, extends backward from the cornea and is 
opaque. The sclerotic and the cornea together form a thick, 
tough covering that supports and protects the delicate structure 
of the eye. 

The choroid coat lies just inside the sclerotic. It consists of 
blood tubes held together with a small amount of connective 
tissue, and extends as far forward as the iris. 

The iris. — The iris is a thin circular curtain with a central 
hole, the pupil. When you look at your eyes in a mirror the 
pupil appears as a dark, round spot in the centre of the colored 
part of each eye. The colored part is the iris. It lies behind 
the cornea, and in front of the lens. Its outer edge connects 
with the choroid; its inner edge forms the margin of the 
pupil. 

The iris contains coloring matter that gives the eye its color. 
It is well known that the color of the eye varies in different indi- 
viduals. Owing to this coloring matter, light cannot pass 
through the substance of the iris, but must pass through the 
pupil in order to reach the retina at the back of the eye. 

The size of the pupil varies from time to time. In a bright 
light the pupil contracts and prevents too much light from 
entering the eye. In a dim light it dilates in order that more 
light can enter. 



THE FIVE SPECIAL SENSES 273 

The lens. — The lens lies behind the pupil. It is clear and 
transparent like glass, and is surrounded by a thin membrane 
called the capsule of the lens. It is convex both on its front and 
on its back surface, and is held in place by the ligament of the 
lens, which is inserted into the choroid coat. 

The aqueous humor.— The watery fluid called the aqueous 
humor fills a small chamber in the front part of the eye between 
the cornea and the lens. The iris divides this chamber into 
two parts. The part that lies between the iris and the cornea 
is called the anterior chamber of the eye; the smaller part that 
lies between the the iris and the lens is called the posterior 
chamber. The anterior chamber communicates with the pos- 
terior chamber through the central hole in the iris, the pupil, 
and both chambers are filled with the aqueous humor. 

The vitreous humor. — The vitreous humor lies behind the lens 
and fills the posterior part of the eyeball. It is a transparent, 
glassy, jelly-like substance, and occupies four-fifths of the eyeball. 

The retina. — The retina is a thin, delicate membrane. It 
forms the inner coat of the eyeball, and extends over the pos- 
terior two-thirds only. Its outer surface rests on the choroid 
and its inner surface on the vitreous humor. 

The retina is the part of the eye that gives us the power of 
vision. All the other parts merely assist the retina in its work. 
The fibres of the optic nerve are spread out in the retina. 
Rays of light that enter the eye and fall on the retina have the 
power to start impulses, which go along the optic nerve to the 
brain and give rise to sensations of sight. 



274 



PHYSIOLOGY FOR YOUNG PEOPLE 



The region of distinct vision. — Not all parts of the retina 
are acted on by light in the same way or to the same extent. 
At the back of the retina, near the centre, is a depression like a 
saucer. This is called the yellow spot on account of its color. 
It is the area of most distinct vision. When you wish to see an 
object distinctly you turn the eyes so as to allow the rays of 
light coming from the object to fall directly upon the yellow 
spot. 

Rays of light falling upon other parts of the retina give rise 
to indistinct vision. If you keep your eyes fixed on a word 

near the middle of a line you 
can see where the line termi- 
nates at either end, and you 
can see the white margins of 
the page beyond, but you do 
not see these things distinctly. 
By means of indistinct vision, 
however, we are made aware of 
the position and movements of 
objects on either side of us 
even while our attention is fixed 
on an object in front of us. 
This is a picture of the back part of the retina. Near the 
centre is the yellow spot where vision is distinct. To the right 
of this is a round spot with blood tubes branching out in all 
directions from it. This is where the fibres of the optic nerve 
enter to be spread out in the substance of the retina. Since 




BACK OF RETINA 

1. Arteries. 2. Veins. 3. Blind spot. 

4. Region of distinct vision 



THE FIVE SPECIAL SENSES 



27.-> 



rays of light that fall on this spot do not give rise to vision it is 
called the blind spot. 

To prove that your eyes have a blind spot, look at the star 
with the right eye while the left eye is closed and the book is 



* 



STAR AND CIRCLE 



held about a foot from the eye. You will then see the star dis- 
tinctly and the circle indistinctly. While keeping your gaze 
fixed steadily on the star, bring the book slowly nearer to the 
eye. The circle will disappear from view just at the moment 
when the rays of light from the circle fall on the place where 
the optic nerve enters the retina; but the circle will reappear 
when the book is brought still nearer to the eye. 

The image on the retina. — In order that we may have dis- 
tinct vision of any object, an image of the object must be 




THE FORMING OF AN IMAGE ON THE RETINA 

formed on the retina. It is only when this image is clear 
and well defined that vision is distinct and satisfactory. 
To obtain a well-defined image, all the rays of light coming 



276 



PHYSIOLOGY FOR YOUNG PEOPLE 



into the eye from any single point must meet at a point on 
the retina. 

In the diagram on page 275 rays of light from the tip A of 
the arrow diverge, or separate, but they are bent, or refracted, 
inside the eye by the lens so as to make them meet again at the 
point A of the image. When the rays meet at the point A 
i ? they are said to be brought 

to a focus at that point. 

In a similar way, rays of 
light from the opposite end 
B of the arrow meet, or 
come to a focus on the 
retina at B. 

The whole surface of the 
arrow on the side toward 
the eye must be considered 
as made up of a great num- 
ber of minute points. Each point sends out diverging rays 
of light, which are made to converge and come to a focus at 
a corresponding point between A and B on the retina. An 
inverted image of the arrow is thus formed on the retina at 
the back of the eyeball. 

The ciliary muscle.— The ciliary muscle is attached to the 
inner surface of the outer coat of the eye, at the junction of the 
sclerotic and the cornea. The fibres of this muscle extend 
backward a short distance and are fastened to the outer sur- 
face of the choroid. When the ciliary muscle contracts, it 




THE CILIARY MUSCLE 
1. Cornea. 2. Iris. 3. Lens. 4. Ciliary 
muscle. 5. Ligament 



THE FIVE SPECIAL SENSES 



277 




MYOPIC EYE 
1. Optic nerve. 2. Rays of light. 3. Focus 



draws the choroid forward. This slackens the ligament that 
connects the choroid with the lens, and allows the front surface 
of the lens to bulge outward. We are then able to see near 
objects more distinctly. 
This change in the lens 
is called accommoda- 
tion. When the ciliary 
muscle relaxes, the cho- 
roid returns to its usual 
position. The ligament 
then tightens, and pulls 
on the front surface of 
the lens, so that this surface becomes somewhat flattened. 
Accommodation of the eye.— When we look at a distant 
object, rays of light from it come to a focus on the retina. When 

we look at a near object, rays 
of light from it will not come 
to a focus on the retina until 
the shape of the lens is changed. 
Far sight and near sight.— 
In the normal eye, rays of light 
from a distant point come to a 
focus on the retina. When an 
eyeball is unusually long from 
front to back, rays of light from a distant point come to a 
focus in front of the retina and diverge again. Confused, in- 
distinct vision for distant objects is the result, but near objects 




HYPERMETROPIC EYE 
1. Optic nerve. 2. Rays of light. 3. Focus 



278 PHYSIOLOGY FOR YOUNG PEOPLE 

can be seen distinctly. This condition is called myopia, or 
near-sight. One cause of myopia in children is injury to the 
ciliary muscle from too much reading or writing, especially in 
a poor light or a bad position. 

On the other hand, when an eyeball is unusually short from 
front to back, rays of light coming into it reach the retina 
before they have time to come to a focus. This condition is 
called hypermetropia, or far-sight Both these defects may be 
overcome by wearing suitable eye-glasses. Eye-glasses are 
lenses made of glass and help the lens of the eye to do work 
that it cannot do alone. 

Color blindness. — Not all persons have the same power to 
distinguish colors. Those that cannot distinguish between 
colors, which to most people are quite different, are said to be 
color blind. Sailors and men employed on railroads and in 
other places where colored lights are used for signals should 
have their eyes tested so as to determine their power to dis- 
tinguish colors. 

Movements of the eyeball.— The eyeballs are moved by 
means of muscles. The picture opposite shows how some of 
these muscles are attached to the eyeball. They are fastened to 
the bony wall at the back of the socket and to the eyeball in 
the front. When, for example, the superior rectus muscle con- 
tracts, the front part of the eyeball is rotated upward, and 
when the inferior rectus contracts, the front part of the eyeball 
is rotated downward. These muscles are hidden from view by 
the membrane that connects the eyelids with the eyeball. 



THE FIVE SPECIAL SENSES 



279 



Tears. — Tears are secreted by the tear glands. Under ordi- 
nary circumstances just enough fluid is secreted to moisten the 
surface of the eyeball and the inner surface of the lids, and is 
carried off by the tear duct which leads into the nose. During 




THE MUSCLES OF THE EYE 
1. Superior rectus muscle. 2. Inferior rectus muscle 



crying or laughing, tears are secreted more rapidly and flow 
over the edge of the lids upon the cheeks, as well as along the 
tear ducts into the nose. 

Care of the eyes. — The eyes are rested by looking at distant 
objects, because then the ciliary muscle is relaxed. When we 
look at near objects for some time the eyes become tired and 
strained, because the ciliary muscle is contracted. When we 
are reading we should stop at intervals and rest the eyes by 



280 PHYSIOLOGY FOR YOUNG PEOPLE 

looking away at something in the distance. This is especially 
true if the light is poor. 

It is important to have a good light when reading, writing, 
sewing, or when looking constantly at near objects of any kind. 
It is never safe to read or work in a dim light, or in a flickering, 
unsteady light. The reading of papers or books in cars often 
causes serious injury to the eyes. It is very fatiguing to the 
eye to read when the moving cars keep jarring the body and 
the printed page. 

When we are reading, the light should come from behind and 
above us. It will then fall upon the page and be reflected to the 
eye. Light thus enters the eye as much as possible from the page 
and as little as possible from surrounding objects. The same 
thing is true of any work we are looking at. We should avoid 
facing a window, mirror, or other bright surface when we are 
reading or working. It is trying to the eyes to read out doors, 
because light enters the eye from every direction. It is also 
more trying to the eyes to read while lying down than while 
sitting or standing. 

Reading by artificial light is more trying to the eyes than 
reading by daylight. Large, plain type does not tire or strain 
the eyes so much as small, indistinct type. It is best to read by 
daylight such books and papers as are printed with poor type 
on poor paper, and to reserve the easiest reading for artificial 
light. 

Many pupils form the habit of holding the book too near the 
eyes. Do not hold the book closer than is necessary. 



THE FIVE SPECIAL SENSES 281 

It is unwise to read much when one is recovering from illness. 
The eyes share in the general weakness of the body and may 
easily be overstrained. 

When the eyes become tired, or the eyeballs ache or burn, it 
is time to stop and give them a rest. 

When cinders or other foreign bodies enter the eye, they 
should be removed at once, if possible. Under such circum- 
stances do not rub the eye, but lift the lids and gently wipe 
away the offending matter with the corner of a clean handker- 
chief. 

SUMMARY . 

1. Pressure against the skin starts impulses that cause sensations of 
touch. 

2. Some parts of the skin are more sensitive to touch than others. 

3. The organs of taste are the tongue and the back part of the mouth. 

4. When the nerve endings in these parts are stimulated, impulses are 
started that cause sensations of taste. 

5. When the endings of the olfactory nerve in the lining of the nostrils 
are stimulated, impulses are started that cause sensations of smell. 

6. The ear consists of the external, the middle, and the internal ear. 

7. Auditory nerves end in the internal ear. When these endings are 
stimulated, impulses are started which cause sensations of sound. 

8. The outer coat of the eye consists of the cornea in front and the 
sclerotic at the back. The inner coats are the choroid and the retina. 

9. The iris is a thin circular curtain with a central hole, the pupil. 

10. The lens lies behind the iris. 

11. The aqueous humor fills the part of the eye that is in front of the 
lens. 

12. The vitreous humor fills the part of the eye that is behind the lens. 

13. Fibres of the optic nerve are spread out in the retina. 



282 PHYSIOLOGY FOR YOUNG PEOPLE 

14. Rays of light coming to a focus on the retina start impulses that 
cause sensations of sight. 

15. When the ciliary muscle contracts, the shape of the lens changes so 
that we may see near objects more distinctly. 

16. The eyes are rested by looking at distant objects. 

17. In reading, the light should come from above and behind. 

18. The book should not be held closer than is necessary. 



PART V— DOMESTIC AND PUBLIC HYGIENE 
CHAPTER XX 

Hygiene explained. — Hygiene is the study of the various 
means of promoting health and vigor, and of preventing disease. 
Good health means greater power to work, greater enjoyment in 
life, and greater freedom from pain. The study of matters that 
affect the health of the individual is called personal hygiene. 

There are many matters in the care and management of a 
home that influence the health of its inmates. The study of 
such matters is called domestic hygiene. 

The cleanliness of streets, the purity of drinking water, the 
safe disposal of sew^age, the isolation of persons ill with conta- 
gious disease are some of the matters that influence the health 
of the people in a community. The study of matters that 
relate to public health is called public hygiene. 

Matters that relate to personal hygiene have been studied at 
considerable length in preceding chapters. Inasmuch as domes- 
tic and public hygiene have so many matters in common, these 
subjects will now be studied together. 

Disease. — It is not wise to allow the mind to dwell too much 

on the subject of disease, or to be unduly anxious regarding the 

probability of contracting an illness. Yet, the healthfulness of 

an individual, a home, or a community is so important that 

283 



284 PHYSIOLOGY FOR YOUNG PEOPLE 

every one should learn the simpler facts concerning the causes of 
disease, and the means of preventing it. 

Remarkable advances have been made in recent years in 
methods of preserving public health. The success already 
achieved shows clearly that many of our common diseases, such 
as consumption, typhoid fever, and diphtheria, may be almost, 
if not entirely, prevented. The chief obstacle in the way of 
their prevention is ignorance or indifference on the part of the 
public. There is good reason for hoping that still greater 
success will result in the future from a wider knowledge of the 
nature of disease and of the means required for its prevention. 

Causes of disease. — There are many causes of disease, but 
nearly all of them may, for convenience, be divided into two 
causes. To the first belong those ailments which have their 
origin within the body. They are due to improper food or 
clothing, over-eating, want of exercise, drinking of alcoholic 
liquor, breathing impure air, or similar mistakes in manner 
of living. All such unhealthful habits and conditions should 
be avoided. 

To the other class belong those ailments that are due to causes 
without the body. Smallpox, measles, scarlet fever, malaria, 
and consumption are familiar examples of this class. All such 
diseases are caused by small animal parasites, or by minute 
plants called germs, or bacteria. 

Animal parasites. — There are a few varieties of animal 
parasites that enter the body and cause disease. Two of these, 
trichina and tapeworm, come from eating raw or insufficiently 



DOMESTIC AND PUBLIC HYGIENE 



285 



cooked pork or beef. The parasite of the tapeworm on entering 
the intestine fastens itself to the wall of the intestine and de- 
velops into the mature worm. The worm lives in the intestine 
where it gives rise to trouble, but is seldom dangerous. The 
trichina attacks the muscles, gives rise to great pain, and often 
causes death. The disease usually comes from eating raw or 




MOSQUITOES 



1. Common mosquito, cvtlex. 2. Mosquito that causes malaria, anopheles. 
3. Mosquito that causes yellow fever, stegomyia 

slightly cooked ham or sausages, but it may come from un- 
cooked pork of any kind. Thorough cooking, so that every 
part of the meat reaches the boiling point, destroys the para- 
sites and prevents these diseases. 

[Malaria, or chills and fever, and yellow 7 fever are caused by 
minute animal parasites that enter the blood from the bite of 
mosquitoes. Only one kind of mosquito, the anopheles, can 
convey the parasite that causes malaria. After the parasite 
enters the body it remains in the blood, and produces in it many 
parasites like itself. In a few days there are so many parasites 



286 PHYSIOLOGY FOR YOUNG PEOPLE 

in the blood that they cause malaria. If an anopheles mosquito 
bites a man who has these parasites in his blood, it may after- 
ward communicate this disease to another person. 

Yellow fever is communicated in a similar way by another 
kind of mosquito, the stegomyia. 

Since the causes of malaria and yellow fever have been under- 
stood, successful attempts have been made to prevent the re- 
currence of these diseases. The best way to prevent them is to 
avoid being bitten by mosquitoes. Doors and windows should 
be screened so as to keep mosquitoes out of the house, and if 
any get in by chance they should be killed. 

Every effort should be made to exterminate mosquitoes in the 
neighborhood. They breed in the water of open rain barrels, 
stagnant pools, swamps, and marshes. Rain barrels should be 
kept covered, swamps and marshes should be drained or filled 
in. If neither can be done, a thin covering of kerosene, known 
as light fuel oil, should be put on the water of these pools every 
two or three weeks. Other kinds of mosquitoes cannot cause 
malaria or yellow fever. But, as others breed in the same places 
with the harmful kinds, the only safe plan is to exterminate all 
mosquitoes, for there is no way of separating one kind from 
another. 

Germs. — Germs belong to the lowest order of plant life and 
consist of a single cell. They are so small that they can be seen 
only with the aid of a microscope, and for this reason myriads 
of them may enter the body unperceived. They are very light 
and float about on particles of dust in the air. 




DOMESTIC AND PUBLIC HYGIENE 287 

Germs grow in the bodies of those who are ill, then pass out 
and are conveyed on bedding, clothing, dust, furniture, food, 
water, or milk, and later infect others. They may enter the 
body by breathing, eating, drinking, or 
through the skin. 

The only way by which anybody can ac- 
quire consumption is by the entry into his 
body of the germs of this disease. In like 
manner, the only cause of typhoid fever is 
the typhoid fever germ; and of diphtheria, 
the diphtheria germ. But the diphtheria typh oid germs 

r to r (Magnified) 

germ cannot cause consumption or any 

disease except diphtheria. Each contagious disease is caused 

by its own kind of germ. 

If you put some corn on a bare schoolroom floor you do not 

expect it to grow. Corn cannot grow without a suitable soil. 

The germs of disease, like other plants, require a soil that is 

suited to them in order to grow. Germs find a suitable soil in a 
body that has become weakened by alcohol, 
by too little food or sleep, by breathing foul 
air, living in dark rooms, lack of exercise, 
and similar causes. As a result, the body is 

one more highly run down, and in its weakened condition 

MAGNIFIED 

germs find a soil in which to grow. 
But when the body is in vigorous health, the germs that enter 
it do little or no harm, because they seldom find in a vigorous, 
healthy body a soil suited to their growth. It is probable that 




288 



PHYSIOLOGY FOR YOUNG PEOPLE 




DIPHTHERIA GERMS 
{Magnified) 



few persons reach manhood or womanhood without, at some 
time, inhaling the germs of consumption. Yet there are many 

persons who do not contract this disease, 
for the conditions in their bodies are 
such that the germs die, and so become 
harmless. 

This natural resisting power of the 
body is its greatest protection against 
the invasion of harmful germs. While 
we do not know all about this power to resist or destroy germs, 
yet we know that it is greatest when we are in good health. 

How germs may be destroyed. — Substances which destroy 
germs are called disinfect- 
ants. All true disinfectants 
are germ-killers. Other sub- 
stances which merely arrest 
or retard the growth of 
germs are called antiseptics. 
Burning in a room brown 
paper, or coffee, sprinkling 
ammonia, perfume, or other 
strong-smelling liquid, may 
hide disagreeable odors, but 
such means will not destroy 
germs or other, causes of 
disease. They merely substitute one odor for another, and 
are called deodorants. 




CONSUMPTION GERMS 
(Magnified) 



DOMESTIC AND PUBLIC HYGIENE 289 

Disinfectants. — There are many ways of destroying germs, 
but no one way is suitable for all cases. Fresh air, continuous 
cleanliness, and freedom from dust assist very greatly in disin- 
fecting a sick-room. One of the best aids is the use of soap 
and hot water on the floor and furniture. 

Boiling water destroys germs of all kinds. This is an easy 
way of disinfecting many articles of clothing and bedding. 
Sunlight and fresh air are nature's means of disinfecting. The 
decay and filth in damp, dark cellars are quickly destroyed 
when brought out to fresh air and light. 

Lime is a cheap and useful disinfectant in cases where it can 
be used. Lumps of quicklime are first slaked by adding to 
them about one-third of their weight of water. This makes 
a powder, or a creamy fluid. One quart of this put into three 
quarts of water makes a good solution. A coating of limewash 
is useful on the walls of cellars, stables, and outhouses. Chlor- 
ide of lime, when mixed with water so as to make a thin solu- 
tion, is a good disinfectant, especially to destroy germs in the 
excreta, i. e., discharges from the bowels and kidneys of persons 
who are ill with infectious diseases. 

Camphenol is a disinfectant that may be used in a great 
variety of ways. It destroys germs, but does not injure clothing 
or furniture. 

For fumigating rooms, the vapor of formaldehyde is a rapid 
and powerful disinfectant and deodorant. 

Isolation. — The object of isolation is to prevent the spread 
of contagious disease from one person, house, or locality to 



290 PHYSIOLOGY FOR YOUNG PEOPLE 

another. The best way is to separate those who are ill with 
contagious disease from all other persons except necessary at- 
tendants. People should be prevented from entering an in- 
fected house until all danger of communicating the disease is 
past. The time during which isolation should be continued 
varies with the severity of the attack and with the kind of illness. 

It is very necessary that all cases of contagious disease, even 
the mildest, should be isolated. No one on account of incon- 
venience, pecuniary loss, or any other reason should seek to 
evade isolation. Humane, conscientious people are willing, 
when they have contagious disease in their homes, to take a 
great deal of trouble to prevent the spread of such disease to 
others. 

COMMON CONTAGIOUS DISEASES 

Diphtheria. — Diphtheria occurs most frequently in children, 
but it often attacks grown people. It is contagious and is 
caused by germs which pass from persons who are ill with the 
disease to others. 

It is not caused by sore throat. A case of ordinary sore 
throat cannot develop into diphtheria unless the germs are 
present. The germs are in the mucus that is coughed up, and 
in all the discharges from the nose and throat. They are often 
present in the saliva that escapes from the mouth while sleep- 
ing. One attack of diphtheria does not make a person less 
liable to a second attack. 

The severity of this disease varies greatly with different in- 
dividuals. It is often so mild that it is overlooked, being mis- 



DOMESTIC AND PUBLIC HYGIENE 291 

taken for a trifling sore throat. It is sometimes so severe that 
the patient's life is in danger in a few hours after the attack 
begins. The germs in the mildest case are infectious, and may 
give rise to the disease in its severest form. 

The mild cases are the ones that cause the disease to spread 
because they are so often overlooked or neglected. Diphtheria 
is frequently spread through schools. The pupils sit near one 
another and often exchange their garments and their toys. 
Children should be warned against exchanging their whistles, 
mouth-organs, strings, candy, gum, half-eaten apples, and, in 
fact, everything that goes into the mouth. They should be 
warned also against chewing the ends of their pencils and pen- 
holders, and should be taught not to put anything into the 
mouth except food and drink. 

The best means for preventing the spread of diphtheria are 
isolation of all cases, the mildest as well as the more severe; 
immediate destruction by burning, or by some other way, of 
all discharges from the nose and throat; and thorough disin- 
fection of all clothing used by the patient, and also of the prem- 
ises after the attack is over. 

Scarlet fever. — Scarlet fever is the most serious of all the 
infectious diseases of childhood. It is very contagious. It 
commonly attacks children, but it may attack adults. 

It is caused by something called a contagium, which is prob- 
ably a germ, and is transferred, in some way, from those who 
arfc ill with the disease to others. This contagium is contained 
in the discharges from the throat and nose, in the scales during 



292 PHYSIOLOGY FOR YOUNG PEOPLE 

peeling of the skin, and also in excreta from the bowels and 
kidneys. 

The contagium may be conveyed on clothing, books, food, 
or on anything touched by the sick while peeling of the skin is 
taking place. It clings for a long time to clothing, bedding, 
furniture, dishes, and may be carried long distances by persons, 
letters, towels, and pet animals, such as cats and dogs, that are 
allowed to come into the sick-room. It may be transferred 
from the sick to the well throughout the entire duration of the 
disease, from the very first symptom to the disappearance of 
the very last. 

Complete isolation of those ill with the disease, and thorough 
disinfection, both during the disease and afterward, are the 
surest ways of preventing the spread of scarlet fever. 

Measles. — Measles is one of the milder diseases of children, 
but it is very contagious. It is caused by something, probably 
a germ, that passes from one who is ill with the disease to those 
who are well. It is not caused by a cold or a sore throat, but 
always by a previous case of measles. 

It is scarcely ever taken more than once; the first attack, 
as a rule, protects the body against another. Because of this, 
ignorant persons sometimes advise exposing a well child to 
measles with the idea that he is sure to have it sometime, and 
it is better to have it over at once. 

No one should ever advocate exposing a child to any disease 
Exposing a child to measles or to any disease is very wrong aiad 
cannot be too severely censured, because every case is a centre 



DOMESTIC AND PUBLIC HYGIENE 293 

of danger from which the disease is liable to spread to others, 
and because very many delicate children between two and five 
years of age die of measles. 

On account of its mildness, the opinion prevails that strict 
quarantine is not necessary in measles. Yet very few diseases 
are so easily communicated from the sick to the well. The 
contagium is carried in clothing, by currents of air, by pet ani- 
mals, and sometimes over long distances by letters. 

Strict isolation of all cases, and thorough disinfection, both 
during the disease and afterward, are necessary to prevent the 
spreading of measles. 

Whooping cough. — Whooping cough is a contagious dis- 
ease. It may affect adults, but it is usually seen in children. 
As a rule, it occurs but once in the same person. 

The contagium of whooping cough is transferred from those 
who are ill to those w r ho are well. It does not develop from a 
cold, or from anything but a previous case. 

Children that have whooping cough should not be allowed to 
attend school, church, or any public gathering, and should be 
kept from other children. 

Infants and delicate children should be carefully protected 
from exposure, because they are the ones in whom the disease 
is most liable to prove serious. 

The discharges from the throat, nose, and mouth of one who 
is ill with w T hooping cough are liable to communicate the dis- 
ease to others. These discharges should be received in vessels 
containing a strong disinfectant, or on soft rags which should 



294 PHYSIOLOGY FOR YOUNG PEOPLE 

be burned immediately. After recovery, there should be care- 
ful disinfection of the room and clothing. 

Small-pox. — Small-pox is a contagious disease. Before the 
discovery of vaccination small-pox was the most virulent and 
fatal of all maladies known to mankind. During the early 
stages the eruption on the skin resembles the rash in chicken- 
pox. 

Whenever small-pox appears in a household or in a 
neighborhood, every one should be vaccinated without delay. 
Isolation of those who are ill, disinfection, and successful vac- 
cination are the best means of preventing the spread of small-pox. 

Typhoid fever. — Typhoid fever is an infectious disease. 
Persons of all ages are liable to take it. It is caused by germs 
that come from a previous case of typhoid fever, and there is 
no other cause of the disease. 

The germs seldom pass directly from the one who is ill to 
those who are well, but they may do so. By far the most 
common mode of conveying the typhoid fever germ is by means 
of drinking water. These germs may get into wells, reservoirs, 
springs, rivers, or lakes, and cause epidemic outbreaks among 
those who drink the water. 

One epidemic in a town in Pennsylvania was caused by a 
single case of typhoid fever that occurred in a cottage on a hill. 
The hill sloped toward a stream that supplied the town with 
drinking water. The patient was ill during January, February, 
and March. The ground was frozen and covered with snow, 
and on this were thrown the discharges of the bowels and kidneys 



DOMESTIC AND PUBLIC HYGIENE 295 

of the patient. During the latter part of March and early April 
there was a thaw and a heavy rain that washed these discharges 
into the stream about sixty feet away. In a short time an 
epidemic of typhoid fever broke out in the town, and of the eight 
thousand inhabitants about twelve hundred took the fever, and 
one hundred thirty died of it. 

Milk may convey the germs of typhoid fever if the cans that 
contain milk are washed with water containing germs. The 
germs grow very rapidly in fresh milk. The germs may be con- 
veyed in ice if it is taken from ponds or streams that are con- 
taminated. Oysters, also, that are fattened in contaminated 
water may convey the disease. 

In some epidemics it has been shown that flies were the 
carriers of the infection. In these cases the excreta of a typhoid 
fever patient were not disinfected, but were thrown out on the 
surface of the soil. Flies then conveyed the germs on their 
bodies to milk and other food that was left uncovered. At all 
times flies should, so far as possible, be kept out of the house. 
Doors and windows should be provided with screens, and all 
food should be kept covered so that flies may not convey to 
it infection of any kind. 

The germs of typhoid fever leave the body along with the 
discharges from the bowels and the kidneys. All excreta from 
a typhoid fever patient should be carefully disinfected accord- 
ing to the directions of the physician or the medical . health 
officer of the district. All clothing and bedding and other 
articles used by the patient should be disinfected. 



296 PHYSIOLOGY FOR YOUNG PEOPLE 

Boiling kills the germs of typhoid fever. Whenever there is 
the least suspicion that drinking water contains the germs it 
should be boiled for a few minutes. 

Consumption. — It is said that more people die from con- 
sumption than from any other disease. It is a disease that 
spreads from one person to another, and any one may catch it. 

Consumption is caused by a germ, the tubercle bacillus, which 
is contained in what is coughed and spit up by one who is ill 
with the disease. If this sputum is allowed to dry, the germs 
mix with the dust, float in the air, and settle on walls, carpets, 
and furniture. They are then breathed in by others and settle 
in the throat and lungs, causing consumption of these parts. 

Consumption or, as it is often called, tuberculosis of the 
lungs is a disease that can be stopped and, therefore, it need 
not spread. The chief means of stopping it is to take care of 
the sputum. It should be kept moist until it can be disinfected 
or disposed of. If the sputum of all persons ill with consump- 
tion were destroyed as soon as it leaves the body, practically 
the only danger of communicating the disease from one person 
to another would be removed. 

If your body is in good health it can resist these germs so 
that they will not cause consumption; but if your body is weak, 

it mav not be able to resist them. 

t/ 

The body may become weakened by alcoholic drinks which 
are among the greatest helpers the germs have, by any form of 
dissipation, by too little food, air, and light, by any severe ill- 
ness, or often by a simple cold. 



DOMESTIC AND PUBLIC HYGIENE 297 

Hie best ways for keeping the body strong are to be in the 

open air as much as possible, to drink plenty of pure water, eat 
plain, wholesome food, keep early hours, sleep eight hours a 
day, and live as regular a life as possible. You should consult 
a doctor when you have a persistent cough, are run down, or 
cannot stand as much work as you could formerly. 

Extract from a Circular issued by the Department of Health, 
City of New York: 

" Consumption is a disease of the lungs, which is taken from 
others, and is not simply caused by colds, although a cold may 
make it easier to take the disease. It is caused by very minute 
germs, which usually enter the body with the air breathed. 
The matter that consumptives cough or spit up contains these 
germs in great numbers — frequently millions are discharged in 
a single day. This matter, spit upon the floor, wall, or else- 
where, dries, and is apt to become powdered and float in the 
air as dust. The dust contains the germs, and thus they enter 
the body with the air breathed. This dust is especially likely 
to be dangerous within doors. The breath of a consumptive 
does not contain the germs and will not produce the disease. 
A person catches the disease from a consumptive only by in 
some way taking in the matter coughed up by the consump- 
tive. 

" Consumption can often be cured if its nature be recog- 
nized early and if proper means be taken for. its treatment. In 
a majority of cases it is not a fatal disease. 

"It is not dangerous to live with a consumptive, if the matter 



298 PHYSIOLOGY FOR YOUNG PEOPLE 

coughed up by him be promptly destroyed. This matter should 
not be spit upon the floor, carpet, stove, wall, or sidewalk, but 
always, if possible, in a cup kept for that purpose. The cup 
should contain water so that the matter will not dry, or, better, 
carbolic acid in a five per cent, watery solution (six teaspoonfuls 
in a pint of water). This solution kills the germs. The cup 
should be emptied into the water-closet at least twice a day 
and carefully washed with boiling water. 

" Great care should be taken by consumptives to prevent 
their hands, face, and clothing from becoming soiled with the 
matter coughed up. If they do become thus soiled, they should 
be at once washed with soap and hot water. Men with con- 
sumption should wear no beards at all, or only closely-cut 
moustaches. When consumptives are away from home, the 
matter coughed up should be received in a pocket-flask made 
for this purpose. If cloths must be used, they should be im- 
mediately burned on returning home. If handkerchiefs be 
used (worthless cloths which can be at once burned are far 
better) they should be boiled at least half an hour in water by 
themselves before being washed. When coughing or sneezing 
small particles of spittle containing germs are expelled, so that 
consumptives should always hold a handkerchief or cloth before 
the mouth during these acts. 

"A consumptive should have his own bed, and, if possible, 
his own room. The room should always have an abundance of 
fresh air — the window should be open day and night. The 
patient's soiled wash-cloths and bed-linen should be handled 



DOMESTIC AND PUBLIC HYGIENE 299 

as little as possible when dry, but should be placed in water 
until ready for washing. 

" If the matter coughed up be rendered harmless, a consump- 
tive may frequently not only do his usual work without giving 
the disease to others, but may also thus improve his own condi- 
tion and increase his chances of getting well. 

"Whenever a person is thought to be suffering from consump- 
tion the Department of Health should be notified, and a medical 
inspector will call and examine the person to see if he has con- 
sumption, providing he has no physician, and then, if necessary, 
will give proper directions as to treatment. 

"Rooms which have been occupied by consumptives should 
be thoroughly cleaned, scrubbed, whitewashed, and painted, or 
papered before they are again occupied. Carpets, rugs, bed- 
ding, etc., from rooms which have been occupied by consump- 
tives, should be disinfected/' 

Tetanus, or lockjaw. — Tetanus is caused by the infection 
of a wound with the tetanus germ. This germ is often present 
in garden soil, and in all kinds of earthy matter, in the dust of 
streets and houses, and on splinters of flooring or on rusty nails. 

The disease frequently occurs because of wounds made 
accidentally by firing blank cartridges, toy cannon, and fire- 
crackers. The germs are usually not contained in these articles, 
but are in the dirt on the hands, or other part of the body, at the 
time of injury. This dirt is carried deeply into the lacerated 
flesh where the germs may find the conditions favorable for 
their growth. 



300 PHYSIOLOGY FOR YOUNG PEOPLE 

All wounds, and especially those contaminated with earth or 
dust of any kind, should be carefully washed and disinfected. 
Blank cartridge and firecracker wounds should be regarded as 
dangerous. They should receive prompt and careful surgical 
treatment. 

Cleanliness.— The healthfulness of any city, town, or dis- 
trict is greatly influenced by the cleanliness of its streets, yards 
and houses; by the purity of the drinking water supplied to its 
inhabitants; and by complete isolation and disinfection in all 
cases of contagious disease. 

Purity of drinking water.— One of the most important 
duties of the officials of a town or city is to provide an abundant 
supply of pure drinking water. 

Fresh water comes from the aqueous vapor of the atmosphere 
and falls to the earth in the form of rain or snow. Some of it 
flows away on the surface into streams or lakes, another part 
sinks into the earth, percolates through the soil, and furnishes 
the water which we obtain from springs and wells. 

Wells and springs near dwellings in villages and in rural dis- 
tricts often contain impurities. In many places great careless- 
ness is shown in regard to the position and management of 
wells. They are often located with only one object in view — 
that of convenience. In choosing a site it should always be 
remembered that wells drain a large area. The water on its 
way to the well percolates through the surrounding soil for a 
considerable distance, and is very liable to convey impurities if 
the soil is contaminated. Often there is not sufficient care taken 



DOMESTIC AND PUBLIC HYGIENE 301 

to prevent domestic animals from polluting wells, the ground 
around them being a favorite resort for cattle and poultry. 
The contamination of wells is a common cause of typhoid fever. 

In villages and rural districts the surface around wells should 
be higher than the surface farther away, so that water falling on 
the ground may drain away from the well and not toward it. 
Wells should be located as far as possible from stables, farm- 
yards, outhouses, and cesspools, in order to avoid polluting the 
drinking water. 

Rivers, streams, and lakes that are situated in thickly in- 
habited districts are very liable to pollution. Such water is 
made impure by the waste and surface water of stables and 
farmyards, by all kinds of refuse from dwellings, and by the 
sewage of towns on their banks. The greatest danger from 
contamination by sewage and household refuse is that it may 
at any time add to the water the germs of typhoid fever or 
other infectious disease. Extreme care should be taken to 
guard the sources of supply in order to keep drinking water 
pure and prevent contamination. 

Filters. — In many large cities, sand filters are used for purify- 
ing water. At the top of the filter there is a layer of fine sand 
varying in thickness from one foot to three or four feet. Below 
the sand is a layer of gravel, which varies from a foot to two feet 
in thickness. Drain pipes are placed under the gravel. The 
water to be purified enters the filter at the top, soaks slowly 
down through the sand and gravel, passes into the drain pipes 
below, and is carried off ready for use. 



302 



PHYSIOLOGY FOR YOUNG PEOPLE 



Such a filter purifies water in two ways. The sand in the 
filter acts as a strainer and removes from the water solid im- 
purities and large numbers of harmful bacteria. In addition 
to harmful bacteria, such as those that cause typhoid fever, 
there are vast numbers of bacteria that are helpful. On the 











-4- 



SETTLING BASIN AND FILTER 
1. Inlet. 2. Settling basin. 3. Filter. 4. Outlet 



grains of sand near the top of a filter are myriads of helpful 
bacteria. These aid very much in purifying water by destroy- 
ing harmful bacteria. 

If water contains a large amount of sediment, it is usual to 
let the water pass first into a settling basin, where the sediment, 
in a few hours, settles to the bottom. If it were allowed to 
enter the filter, the sediment would fill up the minute spaces 
between the grains of sand, choke the filter, and so prevent the 
water from soaking through. 

Removal of refuse. — Refuse from dwellings consists of 
ashes; garbage, consisting of scraps of food, peelings, and other 
kitchen waste; sewage, which includes excreta, and waste water 
from wash-tubs, bath-tubs, sinks, laundries, and rain water 
from the roofs of houses. 

Ashes should not be allowed to accumulate in cellars, or in 



DOMESTIC AND PUBLIC HYGIENE 303 

heaps in back yards, but should be frequently and regularly 
removed from the premises. 

Garbage quickly decays, and, if allowed to remain near the 
house, may pollute both the soil and the air. In many cities 
and towns the garbage is collected regularly and burned. This 
is a satisfactory w r ay of disposing of it. 

Sewage. — The prompt and safe removal of sewage is a 
very important problem. In cities and in many towns it 
is carried away by means of water in underground pipes 
called sewers. All dwellings and premises are connected with 
a sewer by smaller pipes called drains. Drains and sew- 
ers should be carefully constructed and securely fastened 
together to prevent leakage. They should also be ventila- 
ted so that gases, which tend to collect in sewers, may 
escape into the atmosphere. It is also very important that 
in houses all connections of drain pipes with baths, sinks, 
and closets, should be absolutely air-tight, and arranged so 
that no gases can escape into a dwelling from the drains and 
sewers. 

The ultimate disposal of sewage, after it has passed along 
sewers to their outlet, is an exceedingly important matter that 
sometimes fails to receive the attention that it deserves. If 
sewage is allowed to flow into a river and the water of the river 
is aftenvard used for drinking, there is always great danger of 
typhoid fever. In the disposal of sewage some plan should be 
adopted by which contamination of soil and drinking water may 
be avoided. 



304 PHYSIOLOGY FOR YOUNG PEOPLE 

Cleanliness of streets, yards, and houses.— Every thrifty 
housewife dislikes dust, for she regards its presence in a house 
as a sign of poor housekeeping. One problem of good house- 
keeping is to eliminate dust as completely and easily as possible. 
There is a tendency among good housekeepers to "banish the 
broom. " In sweeping a floor with an ordinary house broom, 
much dust is stirred up only to settle again on the floor and all 
articles of furniture. Where floors are made of some smooth, 
hard material, and are wiped frequently with a damp cloth, dust 
is removed more completely, and is not scattered about. This, 
of course, cannot be done where carpets are used. In many 
cases small rugs are better than carpets, for rugs can be taken 
up frequently and cleaned out of doors. In cleaning school- 
rooms, the floors and desks should be wiped with a damp cloth 
every day. 

When carpets and heavy furnishings are used, some kind of 
vacuum process for cleaning is desirable. By this method no 
dust escapes to settle down again, but it is collected and removed. 
This process should be used, in preference to sweeping, in 
cleaning public buildings, such as hotels, clubs, office buildings, 
churches, theatres, and large business establishments. 

All yards and premises should be kept free from rubbish and 
useless material of all kinds. It would be much better if yards 
in the rear of houses were kept as tidy and neat as yards in 
the front are usually kept. 

The healthfulness of all cities is influenced by the condition 
of the streets. It is desirable that streets be paved, for it is 



DOMESTIC AND PUBLIC HYGIENE 305 

difficult to keep unpaved streets clean, especially where there is 
much traffic. Asphalt is the most sanitary paving, because it 
is smooth and impermeable, and may be more easily cleaned 
than any other kind. 



APPENDIX 
EXPERIMENTS 

A few simple experiments with suitable specimens are a 
great aid in teaching physiology. A clearer idea is obtained by 
examining a specimen than by reading many pages of descriptive 
matter. 

A number of good specimens may be obtained without diffi- 
culty. These should be carefully prepared before they are 
brought into the class room. All blood stains and superfluous 
tissue, such as fat, should be removed so as to have the specimens 
as neat and attractive as possible. After they are made ready 
they should be kept in a damp cotton cloth till they are used. 

All that is necessary besides specimens is a sharp knife, a 
pair of scissors, a few large plates, and a supply of towels. It 
will sometimes be necessary for the teacher to procure two 
specimens, and to examine one thoroughly before attempting to 
give a lesson with the other in the class room. 

BONES 

Structure. — Ask a butcher to prepare the shin-bone of a 
sheep or calf by sawing it across the middle, and by sawing 
one of the pieces in two lengthwise. Note the central cavity of 
the shaft, and the ring of solid bone around it. Compare the 

306 



EXPERIMENTS 307 

shaft with the end of the bone, and observe their difference in 
structure. 

Periosteum. — Get a fresh bone and remove all pieces of 
muscle and tendon. Cut across the bone with a sharp knife in 
two places an inch or two apart. Then cut lengthwise from 
one cut to the other and peel off the thin periosteum with the 
point of a knife. Notice how firmly this membrane is attached 
to the bone. 

Compare an old dry bone with a fresh one, and notice their 
different appearance. Small holes may be seen in the surface 
of a dried bone showing where little arteries from the perios- 
teum entered to carry blood for the nourishment of the bone. 

The animal and the mineral part. — To show the animal 
and the mineral part of bone> see the chapter on bones. 

Marrow. — Saw a fresh long bone across and take out marrow 
with a small spoon. It is composed largely of fat and blood 
tubes. 

Bones of spine. — Get the neck of a sheep and boil it for 
two or three hours. Clean off the muscles and ligaments, and 
place the bones in their natural position. You can easily see how 
they fit together, and how the hole in the centre of the bones of 
the spine forms a canal for the spinal cord. 

Joints. — Get a fresh knee-joint from the foreleg of a sheep. 
Have it cut off about three inches above and three inches below 
the joint. This is an example of a hinge-joint. Hinge-joints 
open and close like a hinge of a door. The joints of the finger, 
the elbow, and the knee are examples of hinge-joints. 



308 



PHYSIOLOGY FOR YOUNG PEOPLE 



Cut the joint open and observe the firm, tough ligaments 
which form the side walls of the joint. Notice and collect the 
joint oil, or synovia. Notice, also, the synovial membranes 

which line the inner sur- 
face of the ligaments and 
secrete the joint oil. 

Feel the smooth surface 
of the cartilage that covers 
the ends of the bones. 

The hip-joint of a leg of 
lamb, of a chicken, or of a 
turkey will furnish an ex- 
ample of ball and socket- 
joint. Observe the ball and 
the socket into which the 
ball fits, and also how 
freely the ball can move 
in all directions in the 
socket. Our hip-joints and 
shoulder- joints are ball 
and socket-joints. Notice how much more freely these joints 
move than our own knee and elbow-joints. 

After the lamb, chicken, or turkey is roasted the bones will 
not have the appearance of fresh bones. A fresh ball and 
socket- joint may be obtained from your butcher by asking him 
for the bone he takes out of a fresh ham when he prepares it in 
that way for roasting. 




BALL AND SOCKET OF HIP-JOINT 



EXPERIMENTS 



309 



MUSCLE 



Fresh lean meat of any kind will illustrate the appearance of 
muscle. 

The position and shape of some of the muscles in the lower 
part of the leg of a chicken or turkey may be easily seen. Cut 
off the lower part of the leg 
before it is cooked. Re- 
move the skin and care- 
fully separate the muscles. 
Observe the thin sheets of 
connective tissue that bind 
the muscles together. 
Notice, also, how the 
muscles are attached to the 
tendons. Pull the tendons 
to show how the toes are 
moved. Dissect out one 
of the tendons as far as its 
attachment to the bone. 

Observe the tendons on 
the back of your hand when you open and close your hand. 

Grasp your arm between the shoulder and the elbow, then 
bend the arm at the elbow. You will feel the biceps muscle 
swell up in the middle as it contracts, and become smaller as it 
relaxes. 

The structure of muscle may be shown with corned beef. 




BALL AND SOCKET OF SHOULDER-JOIXT 



310 PHYSIOLOGY FOR YOUNG PEOPLE 

Boil a piece of lean corned beef and you will be able to separate 
the fibres of which the muscle is composed, because boiling 
softens the connective tissue that holds the fibres together. 

FOOD 

Samples of the various kinds of food may be used to illustrate 
the classification of foods. Such of them as can be kept should 
be put into small glass bottles and preserved for future use. 

Proteids. — Among the more common proteids are albumen, 
myosin, gluten, and casein. 

Albumen and myosin.— White of egg is pure albumen. 
Lean meat consists largely of myosin. Scrape a piece of lean 
raw beef. The part that is scraped off consists chiefly of 
myosin. The shreds that remain consist of connective tissue. 
These may be changed into gelatine by boiling. Heat hardens, 
or coagulates, albumen and myosin. Every one is familiar with 
the difference between the white of egg before it is cooked and 
after it is cooked. Drop a little raw white of egg into hot 
water. 

Gluten. — Gluten is a product of wheat. Starch and gluten 
make up the greater part of wheat flour. Put a spoonful of 
flour into one cup and a spoonful of corn-starch into another. 
Add a little water to each. Stir and note the difference between 
them. This difference is due to the gluten in the wheat flour. 

Put a little wheat flour into a small muslin bag and knead it 
well in a basin of water. Note the milky appearance of the 
water when the bag is squeezed. If this water is allowed to 



EXPERIMENTS 311 

stand, the starch in it will settle to the bottom in the form of a 
white powder. Turn the bag inside out and notice the sticky 
yellowish gluten adhering to the muslin. 

Casein. — Casein may be obtained from milk. Take one 
half pint of fresh milk and heat it till it is lukewarm. Add one 
teaspoonful of Fairchild's essence of pepsin, and stir just enough 
to mix. Let it stand until a firm curd of casein is formed. If 
the curd is broken up and strained, a liquid called whey is ob- 
tained. 

Carbohydrates. — The chief carbohydrates are starch and 
sugar. Flour, rice, potatoes, corn-meal, sago, and tapioca are 
common starch foods. 

The best test for starch is iodine. Get an ounce of the tinct- 
ure of iodine at a drug store. A drop put on a little boiled 
starch gives a very dark-blue color, which becomes a beautiful 
light blue when water is added. If any food consisting largely 
of starch is boiled, and a drop of the tincture of iodine is added, 
the blue color that show r s the presence of starch may be ob- 
tained. (For details of experiments, see Physiology and Hygiene 
for Children, page 184.) 

Cut two or three potatoes into thin slices, cover with water, 
and stir the slices about for a few minutes. The water will be- 
come milky, and, if it is allowed to stand, the starch in it will 
settle to the bottom as a w T hite powder. The powder may be 
obtained by pouring off the water. If the powder is cooked, 
and tested with iodine, the blue color that shows starch may be 
obtained. 



312 PHYSIOLOGY FOR YOUNG PEOPLE 

Samples of cane, beet, milk, grape, and maple sugar may be 
obtained for examination. (To test for sugar in milk, see 
Physiology and Hygiene for Children, page 186.) 

Fats. — Show samples of fats. Butter, tallow, and lard are 
obtained from animals. Sweet oil and cotton-seed oil are ob- 
tained from vegetables. Vaseline is a mineral oil. 

Salts. — Procure from a drug store samples of a few of the 
more common salts that are found in food, such as calcium 
phosphate, calcium carbonate, sodium phosphate, sodium car- 
bonate, sodium bicarbonate, potassium chloride, and ferric 
oxide. Compare these with sodium chloride, common salt. 
Samples of these should be kept in small bottles for comparison. 
Pupils will, in this way, become familiar with the use of the 
word salt in its larger meaning. 

DIGESTION 

The teeth. — Procure from a dentist specimens of the different 
kinds of teeth. Observe the root, crown, neck, and the enamel 
covering of the crown. Break a tooth with a hammer and ob- 
serve the pulp cavity and the channels in the roots for nerves. 
Obtain a decayed tooth and break it so as to show how the 
nerve was exposed in the cavity. 

Examine the mouth of a chicken or turkey and note the ab- 
sence of teeth. Examine the gizzard to see how it takes the 
place of teeth. Observe its thick muscles and the tough cover- 
ing of its inner surfaces which fit it for grinding food. Notice 
also any little pebbles that it may contain to aid it in this work. 



EXPERIMENTS 313 

The saliva. — To show that saliva changes starch to sugar, see 
Physiology and Hygiene for Children, p. 187. 

The stomach. — Obtain from a butcher a small piece of the 
wall of a pig's stomach. With the aid of a magnifying glass 
find the openings of the glands that secrete the gastric juice. 

The liver and the pancreas. — A specimen of each from a 
pig or a sheep may be easily shown. 

Pancreatic digestion of milk.— This experiment illustrates 
the action of the pancreas ferment, trypsin, in digesting the 
casein of milk in an alkaline medium. 

Into a quart saucepan put three ounces of water, twelve 
ounces of fresh milk, and fifteen grains of bicarbonate of soda. 
Heat on a gas stove, or in any way that is convenient, to about 
140° F., then divide into two goblets or large tumblers. To 
one of these goblets add ten grains of Fairchild's extractum 
pancreatis, stirring in well, and allow the milk to stand, with 
frequent stirring, for about twenty minutes. 

To show that the casein has been quite thoroughly digested, 
i. e., changed into peptone, as digested proteid .is called, add 
two drachms of acid, either dilute muriatic or acetic, C.P. (the 
latter is generally used). It will then be seen that the milk 
remains fluid, as acids will not precipitate peptone. 

Now, for purposes of comparison, add the same quantity of 
acid to the glass containing the other half of the warm milk 
mixture which has been simply allowed to stand, and stir it up 
slowly from the bottom of the glass. In a few minutes the 
casein will be all gathered into a lump, a hard cheesy mass, 



314 PHYSIOLOGY FOR YOUNG PEOPLE 

showing that the water and soda have no influence in preventing 
coagulation. This illustrates very effectively the value of 
peptonized milk in feeding the sick. 

Pancreatic digestion of starchy foods.— The action of the 
pancreas ferment, amylopsin, may be illustrated in the follow- 
ing way: Dissolve one tablespoonful of Taylor Bros/ Bermuda 
arrowroot in one pint of cold water. Heat with constant stir- 
ring until it comes to a boil, when it will be a perfectly clear, 
smooth starch mucilage. When this mucilage has cooled down 
to about 130° F. pour into a tall tumbler, and sprinkle over this 
ten or fifteen grains of Fairchild's extractum pancreatis, and 
begin to stir with a spatula. The starch on the top will begin 
to liquefy almost immediately, and as the mucilage is stirred 
deeper, it will all liquefy and become as fluid as water. This 
liquefied starch can be poured from glass to glass as if it were 
water, and the change is thus illustrated very prettily. 

To show the action of pepsin on albumen in an acid 
medium. — Take the whites of two fresh eggs, carefully sepa- 
rated from the yolks; add eight ounces of cold water; mix 
thoroughly; heat with constant stirring to the boiling point, and 
boil with constant stirring for at least five minutes, being careful 
not to scorch. Strain through cheese-cloth, without too much 
pressure, so as not to squeeze through any of the hard particles; 
set aside until cold. 

Pour this gelatinized albumen into a glass and add forty 
minims of hydrochloric acid, C.P., and shake well. Put four 
drachms of this acidulated albumen into a test-tube, add two or 



EXPERIMENTS 315 

three grains of Fairchild's scale pepsin; let it stand in a glass of 
warm water, temperature about 130° F. In a few minutes the 

albumen will begin to dissolve. The progressive action of the 

pepsin may he noted by showing the test-tube from time to 
time. 

For comparison, have another test-tube with the same amount 
of albumen mixture, under the same conditions, without the 
pepsin. The contents of one tube will become clear as water, 
the contents of the other will remain opaque like starch jelly. 

To show the action of the emulsive ferment of pan- 
creatic juice. — The characteristic action of the emulsive fer- 
ment is the conversion of oils or fats into a state of minute 
division, or emulsion. 

To show this action of the emulsive ferment add a few grains 
of Fairchild's extractum pancreatis to one or two drachms of 
warm water and one ounce of cod-liver oil, or pure olive oil. 
Shake well and let the mixture stand in a warm place for five 
or six hours. At the end of this time it will be found the oil 
will form a creamy emulsion, if an equal amount of water is 
added and the mixture is well shaken. On standing, this 
emulsion will gradually separate, but may be again emulsified 
by shaking. 

CIRCULATION 

The pulse. — Feel with the fingers for the pulse at the wrist. 
It is best found at a short distance from the base of the thumb, 
and just a little to the outer side of the tendons. Count the 



316 



PHYSIOLOGY FOR YOUNG PEOPLE 



number of beats per minute after you have been quiet for a 
time. Then count the number of beats per minute after a few 
minutes of violent exercise. 

Blood. — Get two jelly jars and fill them with fresh blood — 
or get your butcher to do it. Put a tablespoonful of Epsom 
salts into one while the blood is fresh, and let both stand. The 




FEELING THE PULSE 



blood containing Epsom salts will not clot, but will remain un- 
changed. The blood in the other jar will clot. Examine the 
clot and the serum. 

If possible, examine a drop of blood under a microscope. 

Heart. — Get a sheep's heart from a butcher. Ask him for 
one with the sac still surrounding it, and request him to retain 
the large artery and the veins for two or three inches above the 
heart. 

Cut open the pericardium, the sac which surrounds the heart, 
and notice its smooth, slippery lining. This prevents friction 
between the sides of the heart and the surrounding organs. 



EXPERIMENTS 317 

Find the groove of the heart. You can recognize it by the 
layer of fat which lies upon it. The groove marks the position 
of the septum which divides the right side from the left side. 
Hold the heart so that the groove will be up and the apex will 
point away from you. The part to your right is the right side 
of the heart, and the part to your left is the left side of the heart. 
Squeeze the heart on both sides of the groove with thumb and 
fingers, and notice the thin wall of the right side and the thicker 
wall of the left side. 

Now r hold the heart so that the apex will point downward. 
Cut down through the right auricle on its outer side. Examine 
its interior, and pass the finger dowm through the opening into 
the ventricle below- . Continue the cut down through the wall of 
the right ventricle. Examine the valve between the auricle and 
the ventricle. Pass the finger up under the thin flaps. Notice 
the strings attached to the edge of the flaps and to the wall of 
the ventricle. Find the openings by which the blood enters the 
auricle from the veins, and the opening by which it leaves the 
ventricle. 

Follow the opening into the pulmonary artery until the artery 
divides into a branch for each lung. Cut through the wall of 
this artery and examine the valves that are placed at the begin- 
ning of the artery. 

In a similar w r ay open and examine the left auricle and the 
left ventricle. Notice their valves, and compare the thickness of 
the wall of the left ventricle with the wall of the right ventricle. 
Notice that the septum forms a complete partition between the 



318 PHYSIOLOGY FOR YOUNG PEOPLE 

right and the left side. Follow up the opening from the left 
ventricle into the aorta, and examine the aorta and its valves. 

THE LUNGS 

Secure the heart and lungs of a sheep with the windpipe 
attached. Wash away all traces of blood and remove fat and 
connective tissue. A fresh lung has a beautiful pink color, 
owing to the presence of blood in its capillaries. Note their 
external appearance, the arrangement and number of lobes on 
each side. Feel the lungs and observe the spongy nature of the 
lung tissue. 

Examine the windpipe and its rings of cartilage. Insert the 
nozzle of a bicycle pump into the windpipe and inflate the lungs. 
Scrape away portions of lung tissue from the large bronchial 
tubes, and follow one of these tubes. Observe the divisions of 
the bronchial tube, and also the blood tubes that lie beside them. 

Trace the large blood tube that enters the lung back to the 
heart, and notice which part of the heart it starts from. 

Cut off a small part of the lung substance and observe how 
it floats in water. Why does it float ? 

With a tape line measure the chest of a pupil, on the outside 
of the clothing. Note the size after a full inspiration, and 
again after a full expiration, to show that the chest increases in 
size during inspiration. 

Count the number of respirations in a minute when a pupil 
does not know you are counting. The number averages from 
sixteen to twenty. 



EXPERIMENTS 319 

Expired air contains considerable water in the form of vapor. 
To show this, breathe on a mirror, or on any highly polished 
metal. 

Expired air contains also carbon dioxide. To show this, 
obtain a little lime-water at a drug store. Breathe out through 
a straw, or a glass tube, into a glass of lime-water. The lime- 
water soon becomes milky in appearance because the carbon 
dioxide unites with the lime in the water to form carbonate of 
lime. 

THE BRAIN 

Procure the brain of a sheep and the membranes surrounding 
it, in their natural position. Ask the butcher to be careful in 
sawing the skull and in taking out the brain so that it mav not 
be injured. 

Remove the membranes, and explain that they protect the 
brain, and contain blood tubes which convey blood to nourish 
the brain. 

Notice the deep fissure which divides the brain into tw r o 
equal parts. Observe the wrinkled surface of the brain, and 
pass a pencil along the hollows to show their depth. 

Cut off a part of the brain to show the position of the gray 
matter and of the white matter. 

Look for some of the cranial nerves on the under surface of 
the brain. 

Show how the brain extends downward into the spine as the 
spinal cord. 



320 PHYSIOLOGY FOR YOUNG PEOPLE 

Procure from a butcher three or four inches of the spinal cord 
of an ox to show what it is like. 

How to examine the eye of an ox.— Ask a butcher for two 
fresh eyes. Remove any portions of fat and muscle that may 
be attached to the outer surfaces. Compare the transparent 
anterior part, the cornea, with the opaque posterior part, the 
sclerotic. Note the entrance of the optic nerve at the back. 

Spread a damp cloth on a board and lay the eye upon it, on 
its side. With a sharp knife cut through the sclerotic carefully 
at a point about midway between the edge of the cornea and 
the optic nerve. Let the line of the cut be parallel with the 
edge of the cornea. Enlarge the opening with blunt scissors. 
With care the sclerotic can be cut without injuring the delicate 
inner coats. Next cut through the choroid and the retina, and 
expose the clear glistening vitreous humor beneath. Note and 
compare the color, thickness, and texture of the sclerotic, the 
choroid, and the retina. Squeeze the eyeball gently and expel 
the vitreous humor. The lens may be expelled with the vitre- 
ous humor or it may remain behind. If it remains behind, re- 
move it with the finger. Place the lens on a printed page and 
look through it at the letters. Note its shape. Examine the 
interior surface of the eyeball after the vitreous humor has been 
expelled. Note the entrance of the optic nerve, and also the 
blood tubes at the back, and a dark curtain, the iris, with its 
central hole, the pupil, in the front. 

Take the other eye, and with a sharp knife cut through the 
cornea near its junction with the sclerotic. A small amount of 



EXPERIMENTS 321 

fluid, the aqueous humor, will escape. Compare it with the 
vitreous humor. Extend the cut all the way around the edge 
of the cornea so as to remove it. Compare the cornea with the 
sclerotic. Examine the iris from the front. With a pin, or thin 
splinter of wood, lift up the edge of the iris. Note its color and 
thickness. If the eyeball is squeezed firmly, the lens and the 
vitreous humor may be expelled through the opening in front. 

EMERGENCIES 
WHAT TO DO BEFORE THE DOCTOR COMES 

Accidents happen constantly. Every day some one is cut, 
or burned, or swallows poison by mistake, or falls and is badly 
hurt. As it is not always possible to secure the services of a 
physician immediately in such emergencies, every one should 
learn how to give aid to the injured. 

Burns or Scalds. — The clothing should be removed with 
great care, so as not to cause an increase of pain or to disturb 
the injured parts. The pain may be relieved by covering the 
burned part with cloth that has been wet with a warm solution 
of common baking soda. Apply glycerine, vaseline, lard or 
flour to cover the burned surface and protect it from the air. 
Do not put cold water on a burn. Everything applied to a 
burn or scald, or to any wounded surface, should be perfectly 
clean. 

Clothes on fire. — Very serious injuries are caused by burn- 
ing clothing. If anybody's clothing catches fire, wrap tightly 



322 



PHYSIOLOGY FOR YOUNG PEOPLE 



about him a coverlet, coat, blanket, shawl, rug, table cover, or 
something of the kind that can be had, so as to smother the 
flames. If nothing suitable for wrapping is at hand, have him 




THE POSITION FOR A PERSON WHO HAS FAINTED 

sit or roll on the floor, so as to cover the burning garments with 
his body, and try to smother the flames in that way. 

The person w T hose clothes are on fire should never run — 
running only makes the fire burn more quickly. 

To avoid swallowing flame when the clothing is on fire, one 
should cover the mouth and nose with the arm and lie down on 
the floor. 

Fainting. — A person who has fainted should be placed flat 
on the side or back, with the head as low as the rest of the body, 
or even a little lower. If the body is in this position, blood will 



EXPERIMENTS 323 

flow to the head, and the faintness will pass off in a few min- 
utes. Always allow plenty of fresh air. 

Smelling-salts or camphor may be placed under the nose, 
but are not often required. 

Do not dash cold water on a fainting person. Moisten the 
face with a wet cloth, or apply to the forehead a cloth wet with 
cold water. Do not force anything down the throat of a person 
who is unconscious, for he may in this way be choked to death. 

Fits or convulsions.— Place the patient in a comfortable 
position on the side or back, loosen the clothing so as to allow easy 
breathing, and then avoid moving or disturbing him. If the face 
is red, place the head on a pillow; if it is pale, let the head be low. 

Suffocation. — Suffocation is frequently caused by coal gas 
from a furnace or stove, by gas used for lighting houses, by 
gas at the bottom of old wells or in coal mines, and by the fumes 
of burning charcoal. 

In a case of suffocation from any cause, remove the patient 
at once to the open air, loosen all tight clothing that hinders 
breathing, and moisten the face and chest with cold water. 

Sunstroke. — Remove the patient at once to a cool place, and 
rub the body with ice, or apply plenty of cold water. 

Frostbite. — Rub the frozen part with snow or cold water, 
then wrap it in a wet cloth. The frozen part should never be 
warmed quickly, but always slowly. 

Sting of bees, wasps, and other insects. — Remove the sting, 
if it is left in the wound, and apply ammonia water, a solution 
of baking soda, or a little wet clay. 



324 



PHYSIOLOGY FOR YOUNG PEOPLE 



Snake bites. — If the bite is on the hand or leg, tie a hand- 
kerchief or stout cord loosely round the limb above the wound 
and twist it tightly with a stick, to prevent the poison from being 
carried upward to the rest of the body. Some one should suck 









TO TREAT SNAKE BITE 



the wound as quickly as possible, spitting out what is thus 
taken from the wound. There is no danger in doing this if 
there are no sores in the mouth. 

Dog bites. — If the bite was made by a healthy dog, wash the 
wound with clean cold or hot water, and then apply a pad wet 



EXPERIMENTS 325 

with water. If the (log is known to be mad, treat the bite in the 
same way as a snake bite. 

Cramps. — Sudden, sharp pains in the abdomen are often 
caused by eating unripe fruit, vegetables, or other indigestible 
food. Give castor oil, and apply cloths soaked in hot water, or 
a bottle of hot water, to the abdomen. If these measures fail 
to give relief in a short time, send for a physician. 

Bleeding. — The quickest and safest way to stop bleeding 
from a wound of any kind is to place a finger or thumb directly 
upon the spot that bleeds. 

Moderate pressure on the bleeding spot will stop the bleeding 
at once, whether the blood comes from an artery, from a vein, 
or from capillaries. 

Keep the ringer applied to the wound for ten or fifteen min- 
utes and then remove it slowly. 

If the bleeding begins again, apply the finger once more, and 
continue the pressure until medical aid can be secured. 

Another way to stop the bleeding of a limb is by the use of 
a tourniquet. To make a tourniquet, first tie a knot in the 
centre of a handkerchief or a piece of cloth. Place this knot 
just above the bleeding point, and tie the ends of the handker- 
chief about the wounded limb. Put a stick inside the knot 
that ties the ends and twist hard to get pressure on the blood 
tube that is bleeding. 

Nose-bleed. — Press firmly on the side of the nose from which 
the blood comes, so as to close the bleeding nostril completely. 
At the same time incline the head slightly forward, to keep the 



326 PHYSIOLOGY FOR YOUNG PEOPLE 

blood from running down behind into the throat. If blood 
comes from both nostrils, close them both by pressing firmly 
on both sides. 

If this plan fails, the nostril may be plugged with cotton, or 
with a plug made from a narrow strip torn from a clean hand- 
kerchief or other garment. The strip may be dipped into ice 
water or alum-water, if either is at hand. 

Remove the plug gently after five or six hours. 

If the bleeding begins again, put in another plug and send 
for a physician. 

Be careful to avoid blowing the nose for some time after the 
bleeding stops. 

Foreign bodies in the nose. — If a foreign body, such as a 
pea or a bean, gets into the nostril, blowing the nose may re- 
move it, or it may be hooked out with a looped wire or a hairpin. 

If the first efforts at removal are not successful, leave it alone 
and send at once for a physician. 

Foreign bodies in the ear. — Foreign bodies sometimes get 
into the ear. Insects occasionally crawl into it and cause great 
pain. The delicate drum membrane may be injured unless 
great care is used in removing such bodies. It is therefore 
much safer to have them removed by a doctor. 

Foreign bodies in the eye. — A cinder or a bit of dust on the 
inner surface of the eyelid or on the surface of the eyeball may 
be wiped off easily with the corner of a clean handkerchief, or 
be washed out by bathing the eye. If these simple measures are 
not successful, obtain the aid of a physician without delay. 



EXPERIMENTS 



327 



Foreign bodies in the throat. — Small pieces of food, bones 
or other foreign matter may become lodged in the* throat and 
cause choking. If they are not coughed out quickly, they can 
often be removed with the first finger. 

A few smart slaps on the back between the shoulders, while 
the body is bent forward, will often give instant relief. 

Such foreign bodies as coins, pins, bones, and a great variety 
of similar things, are 
sometimes swallowed 
accidentally. 

In such cases it is 
not wise to give purga- 
tives, nor is it wise to 
cause vomiting. Give 
quantities of mashed 
potatoes and pan- 
cakes, and withhold 
all other food for a day or two. The foreign bodies become 
coated over, if such foods as these are given, and pass along the 
intestine in the natural way without doing harm. 

Broken bones. — A broken bone should be kept as still as 
possible. If it is moved about, the broken ends, which are 
usually sharp and jagged, may injure the surrounding soft parts. 

A patient with a broken bone should not be moved, if he can 
be made comfortable where he is until the doctor comes. The 
injured limb should be supported on a pillow, or anything soft, 
and kept in the position in which it is most comfortable. 




REMOVING A FOREIGN BODY FROM THE 
EYELID 



328 PHYSIOLOGY FOR YOUNG PEOPLE 

Whenever it is necessary to move the patient before the 
doctor comes, it is best to use some form of temporary support 
to keep the broken bone steady and prevent further injury. 




THE DEMI-GAUNTLET BANDAGE (DORSAL) 

From "A Treatise on Surgery" by George Ryerson Fowler, M.D. 

In the fractures of the arm or collar bone, a sling gives all the 
support that is required. If the bone that extends from the 
elbow to the shoulder be fractured, the sling should support the 



EXPERIMENTS 329 

hand and wrist only. If the collar bone or the bones thai ex- 
tend from the elbow to the wrist be fractured, the sling should 
be wide enough to support the whole of the arm below the 

elbow. 

Splints are required when the bones of the leg are broken. 
A thin strip of board, a walking-cane, an umbrella, or any 




FIGURE-OF-8 OF LEG 

From "A Treatise on Surgery" by George Ryerson Fowler, M.D. 

straight stick may be used. Two splints should be employed. 
One should be placed on the outer side of the leg and the other 
on the inner side. The splints should be padded to prevent 
pain from pressure. They may be padded with cotton, pieces 
of cloth, moss, grass, or any soft material at hand; and they 
should be held in place by bandages, handkerchiefs, straps, 
cords, or by strips of cloth of any kind. 

Poisoning. — A physician should be sent for without delay 
whenever poisoning is suspected, but do not wait for the phy- 
sician to come before trying to relieve the patient. 

In most cases of poisoning, the first thing to do is to make the 



330 PHYSIOLOGY FOR YOUNG PEOPLE 

patient vomit, and thus expel the poison from the stomach. 
The exceptions to this rule are where strong acids or alkalis 
have been swallowed. 

In order to produce vomiting, give large quantities of warm 
soap suds, or a mixture of mustard and water, in the propor- 
tion of a tablespoonful of mustard to a pint of water, or salt and 
water, in the proportion of two tablespoonfuls of salt to a glass 
of water. If none of these can be had quickly, give large 
draughts of warm water. 

One or two cupfuls of any one of these simple emetics should 
be swallowed instantly. Then vomiting may be excited by put- 
ting a finger down the throat or by tickling the back part of the 
throat with a feather. As soon as the first attempt at vomiting 
is over, more water, soap suds, mustard and water, or salt and 
water, should be given, and vomiting should be excited again. 

Repeat this several times in order to be sure that all the 
poison is washed out of the stomach. 

Send, in the meantime, for the proper antidote for the poison 
that has been taken, and give it without delay. The following 
is a list of common poisons with their antidotes: 

Sulphuric acid or oil of vitriol. — Give, in a teacup of water, 
two or three tablespoonfuls of any of the following : baking soda, 
magnesia, chalk, whiting, or plaster from a wall. Do not in- 
duce vomiting. 

Oxalic acid, or salts of lemon.— Give, in a teacup of water, 
two or three tablespoonfuls of chalk, magnesia, whiting, lime, 
or plaster scraped from a wall. Do not induce vomiting. 



EXPERIMENTS :;:;l 

Carbolic avid. — Give two or three glasses of milk, followed by 
two or three tablespoonfuls of sweet oil or castor oil. Do not 

induce vomiting. 

Ammonia or hartshorn. — Give four tablespoonfuls of vinegar 
in a teacup of water, or give lemon juice or orange juice, fol- 
lowed by two tablespoonfuls of sweet oil. Do not induce vomit- 
ing. 

Alcohol. — Try to induce vomiting. Give strong coffee, and 
apply cold water to the head. 

Arsenic or Paris green. — Try to induce vomiting. Give three 
or four tablespoonfuls of magnesia in a teacup of water, or give 
castor oil, sweet oil, lime-w r ater, raw eggs and milk. Get dial- 
ized iron from a drug store. Directions for its use accompany 
the preparation. 

Copper or blue vitriol. — Try to induce vomiting. Give w r hite 
of eggs and milk. 

Lead, sugar of lead. — Try to induce vomiting. Give white of 
eggs and flaxseed tea. 

Mercury, bichloride of mercury or corrosive sublimate. — Try to 
induce vomiting. Give milk, white of eggs, and flour in water. 

Opium, or the following drugs which are made from opium 
or contain opium: morphine, laudanum, paregoric, Dover's 
powder, Godfrey's cordial, soothing syrups. — Make the patient 
vomit, and keep him aw r ake by tapping him on the forehead 
with the finger nails, or by striking his face with the end of a 
wet towel. Be very careful not to allow him to become cold. 
Keep him on his feet. Do not let him lie down or sit down. 



332 PHYSIOLOGY FOR YOUNG PEOPLE 

Phosphorus, used in making matches and in rat poison. — 
Try to induce vomiting. Give two or three tablespoonfuls of 
magnesia or chalk in a teacup of water. Avoid giving oil or 
fat. 

Turpentine. — Try to induce vomiting. Give two tablespoon- 
fuls of Epsom salts in half a teacup of water, and large quan- 
tities of flaxseed tea. 

Toadstools and poisonous berries. — Try to induce vomiting. 
Give two tablespoonfuls of Epsom salts in half a teacup of 
water, and castor oil. 

How to avoid poisoning accidents. — These unfortunate ac- 
cidents would scarcely ever occur if all bottles and packages 
containing poison were kept by themselves in a suitable place. 
A bottle of carbolic acid or liniment, for example, should never 
be placed on a shelf beside a bottle of medicine that is intended 
for internal use. It is dangerously easy, especially at night, to 
mistake one for the other. 

Keep all poisons locked up in a place set apart especially for 
them. 

A label, with the name of the contents plainly marked on it, 
should be put on every bottle or package, whether it contains 
poison or not. If the label is lost, throw away the contents of 
the package or bottle. One mistake may cost many times the 
value of what is thrown away. 

What to do in a case of drowning. — In a case of drowning, 
the first thing to do is to get the body out of the water. Unless 
the weather is severe, do not wait to carry the patient to a place 



EXPERIMENTS 



333 



of shelter, but try at once to revive him. There are two things 
that you want to do — restore breathing, and get the body warm. 
Loosen the clothing about the neck and chest, and turn the 




ARTIFICIAL EXPIRATION 



body face down. Then wipe out the mouth and throat with 
your finger, covered with a clean cloth, or handkerchief. 

While the body is face downward place your hands under the 
abdomen, and raise the body until the forehead just rests on the 
ground, so that the water in the mouth and throat may run out. 



334 PHYSIOLOGY FOR YOUNG PEOPLE 

Then turn the body on its back, and place a roll of clothing, 
or something else a few inches high, under the shoulders so as 
to raise the chest. This straightens out the neck, and holds the 
chin away from the chest. 

As the patient lies on his back insensible, the tongue is apt to 
fall back into the throat, and close the air-passage which leads 
from the mouth to the lungs. The tongue, therefore, should be 
carefully drawn well forward, out of the mouth, and held in 
that position, to allow the free passage of air to the lungs. It 
can be held more easily if a handkerchief or cloth is used, as in 
the picture. 

Artificial breathing can then be produced by movements 
which cause the chest to become alternately larger and smaller, 
as in natural breathing. One of the best ways of doing this is 
by Sylvesters method. 

Have some one kneel behind the head of the patient, and 
grasp his arms just below the elbow, then swing them around 
from the body until they are parallel with the head. This move- 
ment causes the chest to become larger. The lungs expand, 
and air goes in to fill them as in natural inspiration. After a 
slight pause, bring the arms back to their first position beside 
the body, and press firmly against the lower ribs. This move- 
ment lessens the size of the chest and forces air out of the lungs, 
as in natural expiration. The movements should be repeated 
about sixteen times a minute, and should be kept up either until 
natural breathing is restored, or until a physician declares that 
the heart has ceased to beat. 



EXPERIMENTS 



335 



Since recovery sometimes lakes place after artificial breathing 
has been kept up for two or three hours, do not be easily dis- 
couraged. Natural breathing commences feebly, and it should 




ARTIFICIAL INSPIRATION 



be aided as much as possible by swinging the arms back at the 
time of natural inspiration, and bringing them down to the sides 
at the time of natural expiration, until the breathing becomes 
strong. 

Natural breathing may be stimulated by holding smelling 



336 PHYSIOLOGY FOR YOUNG PEOPLE 

salts or hartshorn near the nose, but strong hartshorn should 
not be held too close, as it may cause injury to the inside of the 
nose. 

Besides working to restore natural breathing, try in every 
possible way to get the body warm. Have the clothing removed 
as soon as possible, and the body dried gently. Cover it with 
any dry blankets, shawls, or clothing that can be obtained. 
Place along the sides of the trunk and limbs any hot stones, 
bricks, boards or sand that have been heated by the sun, or any 
hot water bottles, or other objects that can be secured. Have 
the limbs and trunk rubbed gently but firmly toward the chest, 
so as to produce warmth, and also to aid the blood in its return 
to the heart. As soon as the patient can swallow, give him fre- 
quently hot drinks, such as tea, coffee, or even water. He may 
also be given, as a stimulant, half a teaspoonful of aromatic 
spirits of ammonia in a tablespoonful of water, every half hour, 
till the feet and hands become warm, and the patient feels com- 
fortable. When he feels well enough to be removed, he should 
be carried carefully, with head low, and put into a warm bed. 
Some one should remain with him for a while so that prompt 
measures may be taken if breathing should again stop. 

HINTS FOR THE SICK-ROOM 

Choice of the sick-room. — The sick-room should be the 
brightest and most cheerful room in the house. Fresh air, 
sunshine, and freedom from noise are the most important points 
to consider in making selection of a room. Choose a large, 



KXPKUIMENTS 337 

well ventilated room into which the sun shines. If possible, it 
should have two windows, one facing the south. An open 
fireplace is always desirable in a sick-room, because it 
allows a constant current of fresh air to enter and foul air to 
escape. 

Preparation of the sick-room.— The sick-room should con- 
tain no unnecessary articles of furniture. Two chairs, one or 
two small tables, and a comfortable bed for the patient are 
usually sufficient. Remove all heavy drapery and thick cur- 
tains from the windows, for they obstruct the free entrance of 
air and shut out the sunlight. 

In contagious diseases, such as diphtheria, measles and 
scarlet fever, the carpets should be taken up and articles of 
clothing should not be allowed to remain in the sick-room. A 
few pictures may be left on the walls, as they are restful to the 
eye and give the room a cheerful appearance. 

Care of the sick-room.— The sick-room should be kept 
clean and tidy. Offensive matters should not be allowed to 
remain in the room, but should be removed promptly. Never 
allow soiled clothing or bed-linen to accumulate, but remove 
them from the room as soon as they are changed. 

Fresh flowers always make a room look cheerful, but care 
should be taken to select those having an odor that is not un- 
pleasant to the patient. 

It is often difficult to keep the air in a sick-room pure, and at 
the same time to avoid a draft. In summer the windows may 
be left open day and night. Excessive currents of air may be 



338 PHYSIOLOGY FOR YOUNG PEOPLE 

avoided by means of screens placed between the patient and 
the windows. In winter, the lower sash of the window may be 
raised four or six inches, and the space under it may be closed 
with a board. Air will then pass in between the upper end of 
the lower sash and the lower end of the upper sash. 

It should always be remembered that it is as important to 
have fresh air in winter as it is in summer, and that it is even 
more important to have a plentiful supply of fresh air during the 
night than during the day, because air at night is made impure 
also by lamps or gaslight. The air is usually colder during the 
night than during the day, but in other respects night air is 
practically the same as day air. 

Care of the patient. — It is always desirable that one person 
should have entire charge of the sick-room, and should under- 
take the responsibility of carrying out the physician's orders. 
A good nurse will follow faithfully the directions given by the 
physician. The directions regarding food, treatment, and 
medicine should be written down in order that they may be 
carried out punctually and that mistakes may be avoided. 

The person in charge of the sick-room should have regular 
hours for rest, meals, and exercise out-of-doors, for no nurse 
can do her work well and be cheerful when she is overtired. 
During her absence written orders should be left for those in 
attendance so as to prevent mistakes. 

The comfort of the patient depends much upon the nursing. 
The work in the sick-room should be done quietly and cheer- 
fully, without undue haste or excitement. The nurse should 



EXPERIMENTS ' 339 

avoid talking too much, and should never weary the patient by 
describing her own trifling ailments and troubles. 

A kind, sympathetic tone, gentleness in touch and move- 
ments, and a mind that is quick to appreciate the needs of the 
patient are qualities that are always highly prized in a nurse. 




KEY TO THE PICTURE ON PAGE 8. 
u\ windpipe ; 6, breastbone ; r, ribs ; {, lungs ; lr, liver ; s, stomach ; i, intestine. 




KEY TO THE PICTURE ON PAGE 9- 

&, blood tubes ; h, heart ; p, partition between chest and abdomen ; I, liver ; s, stomach ; 

i, intestine. 



GLOSSARY 

Ab-do'men. — The lower part of the trunk. 

Ab-sorp'tion. — The passing of food from the intestine into the blood tubes. 

Ad'en-oid growths. — Small growths at the back of the nasal passages. 

Al-bu'men. — A kind of proteid, as white of egg. 

Al-i-men'ta-ry ca-nal'. — The tube in which food is received and digested. 

A-mce / ba. — One of the simplest animals known. 

An-ti-sep / tic. — Anything that restricts the growth of germs. 

A-or'ta. — The great artery that starts from the left side of the heart. 

A'que-ous hu'mor. — A watery substance in the front part of the eyeball. 

Ar'ter-y. — A blood tube through which blood flows away from the heart. 

Asth'ma. — A disease that causes difficult breathing. 

Au'ri-cle. — A chamber of the heart that receives blood from the veins. 

Bac-te'ri-a. — Microscopic plants. Some of them cause diseases. 
Brain. — The central organ of the nervous system. 

Cap'il-la-ries. — Very small blood tubes that connect the arteries and the 
veins. 

Car-bo-hy'drates. — Another name for starch and sugar. 

Car'bon-di-ox'ide. — A colorless gas formed by respiration and also by fer- 
mentation. 

Car'di-ac o'pen-ing. — The opening from the esophagus into the stomach. 

Car'ti-lage. — Gristle . 

Ca'se-in. — A proteid found in milk, from which cheese is made. 

.Cells. — The microscopic parts of living matter, of which the whole body is 
formed. 

Cel'lu-lose. — The chief substance in the wall of vegetable cells. 

Cer-e-bel'lum. — The lower and back part of the brain. 

Cer'e-brum. — The upper and front part of the brain. 

Choroid. — The middle coat of the eyeball. 

Chyle. — A milky fluid in the lacteal tubes and the thoracic duct. 

Chyme. — The soup-like contents of the stomach and intestine. 

343 



344 GLOSSARY 

Cir-cu-la'tion. — The movement of blood through the blood tubes. 

Clav'i-cle. — The collar bone. 

Co-ag-u-la / tion. — A change from a liquid to semi-solid state; a curdling. 

Con-ta'gious di-seas'es. — Diseases that one may take from another. 

Cor'ne-a. — The transparent coat at the front of the eyeball. 

Cor'pus-cles. — Minute cells in the blood. 

Cra'ni-al nerves. — Nerves connected with the brain. 

Cra'ni-um. — The part of the skull that holds the brain. 

Dermis. — The inner layer of the skin. 

Di'a-phragm. — The muscular partition between the thorax and the abdo- 
men. 
Dis-in-fec / tant. — A substance that destroys germs. 
Dis-lo-ca'tion. — The wrenching of bones out of position at a joint. 

Ear drum. — A thin membrane that separates the external from the middle 

ear. 
E-mul'sion. — A milk-like preparation of oil and water. 
Ep-i-der'mis. — The outer part of the skin. 

Ep-i-glot'tis. — A small lid that covers the opening into the windpipe. 
Ep-i-the'li-um. — A layer of cells covering internal and external surfaces of 

the body. 
E-soph'a-gus. — The tube through which food passes from the mouth to 

the stomach. 
Eu-sta'chi-an tube. — A small tube that extends from the throat to the 

middle ear. 
Ex-cre'tions. — Waste matters. 
Ex-pi-ra'tion. — The act of breathing out air from the lungs. 

Fer-men-ta'tion. — The process by which one substance is changed into an- 
other by ferments. 
Fil'ter. — A strainer for removing impurities from water. 
Function. — The special work of an organ or part of the body. 

Gang / li-on. — A small cluster of nerve-cells. 

Gastric juice. — A thin, acid fluid made from the blood by the glands of 

the stomach. 
Glot'tis. — The opening from the throat into the windpipe. 
Glu'ten. — A proteid found in wheat and some other grains. 



GLOSSARY 345 

Hair fol'li-cle. — A little pit in the skin in which the root of the hair grows. 
Ha-ver'sian ca-nals'. — Channels in bone substance for small blood tubes. 
Hu'mer-us.— The bone between the shoulder and the elbow. 
Hy'dro-gen. — A eolorless gas forming, by volume, two-thirds of water. 

In-spi-ra'tion. — The act of breathing air into the lungs. 

In-tes'tine. — The part of the alimentary canal that is below the stomach. 

I'ris. — A thin colored curtain in the front part of the eye. 

Ir-ri-ta-bil / i-ty. — The power of responding to a stimulus. 

Is-o-la'tion. — Separation. 

Kid'neys. — The organs that take urine from the blood. 

Lac'te-als. — Small tubes that carry fat from the intestine to the lymph 

tubes. 
Lactic ac'id. — The acid formed when milk sours. 
Lar'ynx, or Ad'am's ap'ple. — The enlarged part of the windpipe. It is the 

organ of the voice. 
Lig'a-ment. — A band of white connective tissue that joins bones together. 
Liv'er. — The largest gland in the body, situated beneath the diaphragm on 

the right side of the body. 
Lock'jaw, or Tet'a-nus. — A disease in which there is stiffness or spasm of 

muscles. 

Mal'tose. — The kind of sugar that is made w T hen saliva acts on starch. 

Me-dul'la. — The lowest part of the brain. 

Mem'brane. — A thin layer of tissue. 

Mi'cro-or'gan-ism. — A body so small that we can see it only with a micro- 
scope. 

Mu'cous mem'brane. — The thin covering lining the mouth, alimentary 
canal, and other cavities in the body that communicate with the air. 

My'o-sin. — The kind of proteid contained in lean meat. 

Nar-cot'ic. — A drug w T hich, in small doses, produces sleep, and in large 

doses produces stupor or even death. 
Nerve-cell. — The enlarged part of a nerve cell. It receives and sends out 

nerve impulses. 
Nerve-fibres. — Fine thread-like projections that extend from the nerve-cells. 
Nerves. — Long bundles of nerve-fibres w r hich carry messages to different 

parts of the body. 



346 GLOSSARY 



Nic'o-tine. — A poison contained in the leaves of tobacco. 
Ni'tro-gen. — A colorless gas forming about 79 per cent, of air. 
Ni-trog'en-ous food. — Food that contains nitrogen. 
Nu'cle-us. — A small body within the protoplasm of the cell. 
Nu-tri'tion. — The process by which the body is nourished by food. 

Or'gan. — A part of the body that has a special work, or function. 
Ox-i-da'tion. — The uniting of some substance with oxygen. 
Ox'y-gen. — A colorless gas forming about 21 per cent, of air. 

Pan'cre-as. — A gland behind the stomach. 

Pa-pil'la. — A small elevation of the true skin. 

Par'a-sites. — Animals or plants that procure nourishment from, and live 
on, other animals or plants. 

Par-ot'id glands. — The salivary glands that lie in front of the ears. 

Pas-teur'ize. — To destroy germs in milk by heating it until it reaches a 
temperature of about 150° F. 

Pa-tel'la. — The kneecap. 

Pel' vis. — A bony ring that supports the spine and rests upon the thigh bones. 

Pep'sin. — A ferment contained in gastric juice 

Per-i-car'di-um. — The sac surrounding the heart. 

Per-i-os'te-um. — A dense membrane covering the whole surface of bone. 

Per-i-stal / tic move'ments. — Movements caused by the contraction of mus- 
cles in the stomach and intestine. 

Phar'ynx. — The part of the alimentary canal between the mouth and the 
esophagus. 

Phys-i-ol'o-gy. — The study of the functions performed in living things. 

Plas'ma. — The watery part of the blood. 

Pleu'ra. — A serous membrane covering the lungs. 

Pneu-mo'ni-a. — A disease in which there is inflammation of the lungs. 

Por'tal cir-cu-la'tion. — The movement of blood through the liver. 

Pro'te id. — A food used for the building of body tissue. 

Pro'to plasm. — The principal substance in an animal or a vegetable cell. 

Pty'a-lin.— The ferment in saliva. 

Pulse. — The throb of arteries as blood is forced through them by the heart. 

Pu'pil. — The small hole in the iris, through which light enters the eye. 

Py-lo / rus. — The opening from the stomach to the intestine. 

Pyr'e-thrum. — A plant from whose flowers insect powder is made. 



GLOSSARY 347 

Re-flex 7 action. — An action thai Is involuntary. 

Ren'net. — A ferment that is secreted by the stomach. It curdles milk. 

Ret'i-na. — The inner coat oi the eyeball. 

Rheu'ma-tism. — An acute disease that causes pain in the joints or muscles. 

Sa-li'va. — The digestive fluid secreted by the salivary glands. 

Scap'u-la. — The shoulder blade. 

Scle-rot'ic. — The white, outer coat at the back of the eyeball. 

Serous mem'brane. — A membrane lining a cavity of the body from which 

there is no outlet to the surface. 
Sew'age. — Liquid waste matter. 
Skel'e-ton. — The bony framework of the body. 
Skull. — The bony box that covers and protects the brain. 
Spi'nal col'umn. — The backbone. 
Spi'nal cord. — The part of the nervous system that extends down within 

the backbone. 
Spore. — A spore corresponds to a seed in other plants. 
Sprain. — A straining or twisting of the ligaments of a joint. 
Sternum. — The breast bone. 
Stomach. — A muscular sac, or enlargement of the alimentary canal, in 

which digestion is carried on. 
Sub-lingual glands. — The salivary glands beneath the tongue. 
Sym-pa-thet'ic nerves. — Nerves that carry impulses to involuntary muscles. 
Syn-o'vi-a. — A fluid that lubricates the movable joints. 
Sys-tem'ic cir-cu-la'tion. — The movement of the blood through all the body 

except the lungs. 

Ten'don. — A strong cord or band of connective tissue to which the end of 

a muscle is attached. 
Tho-rac'ic duct. — A tube in front of the spine that conveys lymph to veins 

leading to the heart. 
Thorax.— The chest. 

Tis'sue. — One of the kinds of material that make up an organ. 
Tra-che'a. — The windpipe. 
Tu-ber-cu-lo'sis. — A germ disease that may affect any part of the body. 

U-re'a. — The chief waste product of proteid. It is excreted in the urine. 

Ve'nous blood. — The dark blood in the veins. 



348 GLOSSARY 

Ven-ti-la'tion. — The process of removing impure air and supplying fresh air. 
Ven'tri-cle. — A chamber of the heart that receives blood from an auricle. 
Ver'mi-form ap-pen'dix. — A worm-like projection that hangs down from 

the large intestine. 
Ver'te-bra. — One of the bones that make up the backbone. 
Vil'li. — Hair-like projections from the inner surface of the small intestine. 
Vit' re-ous hu'mor. — A thick glassy substance inside the eyeball. 

Wind'pipe. — The tube extending from the throat to the lungs. 

Yeast. — The agent causing fermentation that produces alcohol from sugar. 



INDEX 



Abdomen, 10, 67, 90. 

Accommodation of eye, 277. 

Adenoids, 130. 

Air, 123, 134, 135. 

Air sacs, L24, 132. 

Air tubes of insects, 64. 

Albumen, 16. 

Alcohol, 35, 43, 115. 

effect on stomach, 87. 
" liver, 88. 
" " circulation, 110. 
" heart, 111. 
" lungs, 139. 
" " growth, 139. 

" skin, 162. 
" " temperature, 164. 

" kidneys, 164. 
" " muscle, 201. 
" " nervous system, 253. 
" employment, 11, 27, 
120. 
Alimentary canal, 57, 58, 67. 
Amoeba, 4^, 55, 220. 
Anatomy, 11. 
Antiseptic, 288. 
Aorta, 94, 96, 101. 
Appendix, 80. 
Aqueous humor, 271. 
Areas of cerebrum, 233, 234. 
Arteries, 91, 94, 96, 106, 127, 143, 

149. 
Auditory nerves, 267. 
Auricle/ 92, 94. 

Bacteria, 19, 105, 170. 



Ball-and-socket joint, 188. 

Bathing, 152. 

Beef tea, 33. 

Bile, 80, 82. 

Blind spot, 275. 

Blood, 6, 91, 98, 101, 103, 108, 148, 

235. 
Bone, 6, 174, 177, 195. 
Boston ivy, 219. 
Brain, 106, 208, 212, 226, 227, 231, 

247. 
Bread, 34. 
Broken bones, 191. 
Bronchial tubes, 124, 127. 
Butter, 23, 36. 

Camel, 61. 

Capillaries, 84, 91, 94, 96, 101, 127, 

132, 143. 
Carbohydrate, 20, 22, 25. 
Carbon dioxide, 44, 50, 65, 132. 
Cartilage, 6, 181. 
Caseinpgen. 17. 
Cell, 3, 49, 86, 105. 
Cerebellum, 232, 233, 234. 
Cerebrum, 232, 233. 
Chocolate. 27. 
Choroid. 271, 272. 
Chyle, 86.. 
Chyme, 80. 

Cigarettes, 204, 258, 262. 
Ciliary muscle, 276. 
Circulation, 57, 5S, 91. 
Clavicle, 182. 
Clothing, 158. 



349 



350 



INDEX 



Clotting of blood, 108. 

Coffee, 27. 

Colds, 155, 156, 157. 

Cold bath, 153, 157. 

Cold blooded animals, 151. 

Colon, 79. 

Color blindness, 278. 

Composition of bone, 185. 

Connective tissue, 6, 88, 164. 

Consumption, 296. 

Control, 215, 229. 

Convolutions, 231. 

Cooking, 31. 

Corpuscles, 104, 105, 106, 108, 132, 

133. 
Cortex, 233, 234. 
Cotton, 159. 
Cranial nerves, 236. 
Cranium, 180. 
Crawling, 173. 
Cricoid cartilage, 131. 
Croup, 124. 

Deodorant, 288. 
Dermis, 131, 143. 
Diaphragm, 10, 67, 82, 129. 
Digestion, 67. 

in mouth, 68. 

" stomach, 74. 

" intestine, 79. 
Diphtheria, 290. 
Disease, 283. 
Disinfectant, . 288. 
Dislocation, 190. 
Distilled liquors, 46. 
Drowning, 138. 
Duodenum, 79. 

Ear, 267. 

Earthworm, 56, 62, 224. 
Eating, 14, 36, 40. 
Emergencies, 321. 
Enamel, 69. 



Epidermis, 141. 

Epiglottis, 74. 

Epithelium, 5. 

Esophagus, 10, 57, 60, 67, 73, 224. 

Exercise, 207. 

Experiments, 306. 

Eye, 271. 

Eye-strain, 250. 

Fainting, 322. 

Fat, 6, 21, 23, 36. 

Fatigue, 209. 

Femur, 183. 

Ferment, 43, 44, 45, 72, 77, 81, 82. 

Fermentation, 43, 44, 45, 46. 

Fibrin, 108. 

Fibula, 183. 

Filter, 301. 

Flies, 39, 295. 

Flying, 173. 

Frog, 64. 

Function, 1, 7. 

Games, 210, 211. 

Ganglion, 224, 246. 

Gastric juice, 31, 76. 

Germs, 18, 19, 25, 31, 170, 286. 

Gills, 63. 

Gizzard, 57, 59. 

Gland, 59, 86. 

salivary, 70. 

gastric, 76. 

pancreas, 80. 

liver, 82. 

sweat, 145. 

oil, 147. 

tear, 279. 
Glottis, 74, 131. 
Gluten, 17, 21. 
Glycogen, 86, 88. 
Growth, 15, 52, 139. 
Gymnasium, 210, 212. 



INDEX 



351 



Habit, 242. 

Hair, 146. 

Haversian canals, 187. 

Headache, 250. 

Hearing, 267. 

Heart, 58, 85, 91, 98, 103, 111, 132, 

200, 208, 259. 
Heat, 15, 20, 50, 148, 201. 
Hibernate, 151. 
Hinge joint, 188. 
Humerus, 182. 
Hygiene, 11, 37, 38, 39, 40, 41, 103, 

191, 247, 270, 279, 283. 

Indian corn, 217. 
Insects, 63, 224. 
Intestine, 10, 58, 68, 79. 
Intestinal juice, 80, 83. 
Invertebrate, 224. 
Involuntary muscle, 200. 
Iris, 272. 
Irritability, 215. 
Isolation, 289. 

Jelly-fish, 55, 221. 
Joints, 188. 

Kidney, 65, 96, 133, 160, 164. 

Lacteal, 84, 86. 

Larynx, 123, 130. 

Lens, 273. 

Life insurance, 255. 

Ligament, 189. 

Lime, 289. 

Lincoln, Abraham, 47. 

Linen, 159. 

Liver, 10, 82, 86, 88, 96. 

Lockjaw, 299. 

Locomotion, 170. 

Loss of heat, 149, 150. 

Lungs, 7, 10, 127, 132, 139, 160, 208. 



Lymph, H5 f 86, 101, 108. 
Lymph tubes, 108. 

Malaria, 285. 

Malt liquors, 46. 

Maltose, 72. 

Marrow, 187. 

Mastication, 68. 

Measles, 292. 

Medulla, 232, 234. 

Milk, 17, 18, 19, 36, 43. 

Morphine, 260. 

Mosquitoes, 285. 

Motor nerves, 240. 

Movement, 168. 

Mucous membrane, 74, 84, 87. 

Mucus, 75, 87. 

Muscle, 6, 77, 83, 86, 91, 94, 174, 

195, 207, 222, 235, 278. 
Muscular sense, 265. 
Mussel, 223, 224. 
Myosin, 17. 

Nails, 147. 

Narcotics, 11, 117, 259. 

Nautilus, 171. 

Nerve ring, 225. 

Nerve tissue, 7. 

Nerves, 106, 143, 175, 197, 215, 222, 

236, 237, 243. 
Nicotine, 256, 258, 259, 260. 
Nucleus, 4. 
Nutrition, 49. 

plant, 49. 

animal, 55. 

Oil glands, 147, 152. 
Olfactory nerves, 266. 
Olympian games, 111, 112. 
Opium, 260. 
Organ, 7. 
Overeating, 38. 



352 



INDEX 



Oxidation, 52, 53, 61, 86, 89, 116, 

148, 208. 
Oxygen, 62, 106, 123, 132, 133. 

Pancreas, 80. 

Pancreatic juice, 80, 81, 83. 

Papilla?, 143, 146, 265. 

Parasites, 31, 284. 

Patella, 183, 

Pelvis, 184. 

Pepsin, 77. 

Pericardium, 92. 

Periosteum, 187. 

Peristaltic movement, 77, 83. 

Perspiration, 145, 149, 157, 208, 235. 

Pharynx, 67, 73. 

Physiology, 3, 11. 

Plasma, 104, 106, 108. 

Pleura,. 127. 

Pores, 50, 53, 146. 

Portal circulation, 101. 

Proteid, 16, 21, 23, 25, 36, 77, 85, 

104. 
Protoplasm, 4, 53, 55, 65, 88, 139, 

216, 220. 
Ptyalin, 72, 81. 
Pulmonary circulation, 99. 
Pulse, 102. 
Pylorus, 74. 

Radius, 182. 

Reflex actions, 240, 243. 

Rennet, 77. 

Retina, 271, 273. 

Root-hairs, 50, 52. 

Rum, 46. 

Saliva, 31, 59, 70, 80. 
Salivary glands, 70, 80. 
Salmon, 171. 
Salt, 24, 25, 36, 104. 
Scapula, 182. 



Scarlet fever, 291. 

Sclerotic, 271. 

Sensation, 233. 

Sensitive plant, 169. 

Sensory nerves, 240. 

Serous membrane, 92. 

Serum, 108. 

Sewage, 303. 

Sick-room, 336. 

Sight, 271. 

Silk, 159. 

Skeletal muscles, 198. 

Skeleton, 177. 

Skin, 141, 160, 162, 208, 235, 

264. 
Skull, 180, 231. 
Sleep, 235, 249. 
Sleep movements, 169. 
Smallpox, 294. 
Smell, 266. 
Sound, 132, 267. 
Soup, 33. 

Special senses, 264. 
Spinal column, 179, 181, 226. 
Spinal cord, 106, 226, 237, 238, 240, 

242. 
Spinal nerves, 237. 
Spine, 179, 180, 181, 226. 
Spores, 19, 44. 
Sprains, 190. 
Starch, 20, 22, 31, 36, 46, 51, 54, 72, 

80. 
Sternum, 181. 
Stimulus, 215, 216, 217, 218, 220, 

244. 
Stomach, 10, 56, 58, 59, 60, 61, 68, 

74, 76. 
Suffocation, 138. 
Sugar, 20, 21, 25, 36, 43, 44, 45, 46, 

72, 85, 86, 104. 
Sundew, 219, 220. 
Suture, 180. 



INDEX 



3,53 



Sweat glands, 145. 
Swimming, 171. 
Sympathetic nerves, 244. 
Synovia, 189. 
Systemic circulation, 100. 

Taste, 265 

Tea, 27. 

Tears, 279. 

Tendons, 196. 

Thoracic duct, 86, 107, 108. 

Thorax, 92. 

Thyroid cartilage, 130. 

Tibia, 183. 

Tissues, 5. 

Tobacco, 11, 29, 112, 113, 165, 205, 

256, 261. 
Tongue, 265. 
Tooth, 68, 69. 
Touch, 264. 
Trachea, 123. 
Tuberculosis, 189, 296. 
Typhoid fever, 294. 

Ulna, 182. 

Urea, 65, 160, 161, 165. 



Valve, 93, 94. 

Veins, 91,94, 96, 127. 

Ventilation, 134, 135, 136, 137, 157. 

Ventricle, 92, 93, 94, 90. 

Venus 's fly-trap, 219. 

Vertebra, 179, 180. 

Vertebrate, 225. 

Villus, 84. 

Virginia creeper, 218, 219. 

Vitreous humor, 271, 273. 

Vocal cords, 131. 

Voice, 130. 

Voluntary muscles, 198, 233. 

Warm bath, 152. 

Warm blooded animals, 150. 

Waste matter, 65, 133, 160. 

Water, 25, 26, 36, 38, 45, 51, 300. 

Whiskey, 46. 

Whooping cough, 293. 

Windpipe, 7, 10, 123. 

Wine, 45. 

Wool, 158. 

Yeast, 44. 
Yellow fever, 286. 
Yellow spot, 274. 



